Here are the classes, structs, unions and interfaces with brief descriptions:

Nquentier
Nenml
Nconversion_rules
CISkipRule	The ISkipRule interface describes a conversion rule with regards to which some ENML/HTML element/attribute should be skipped during the conversion
CISkipRuleBuilder
CIConverter	The IConverter interface encapsulates a set of methods performing conversions between ENML and other note content formats, namely HTML
CIDecryptedTextCache
CIENMLTagsConverter	The IENMLTagsConverter interfaces provides methods which convert Evernote-specific markup tags such as en-crypt, en-media etc. into their counterparts which should be used in the HTML representation of note content
CIHtmlData	The IHtmlData represents the result of ENML to HTML conversion: HTML itself plus some metadata
Nlocal_storage
Ntests
Nmocks
CMockILocalStorage
CILocalStorage
CListObjectsFilters
CListGuidsFilters
CListOptionsBase
CListNotebooksOptions
CListLinkedNotebooksOptions
CListSavedSearchesOptions
CListNotesOptions
CListTagsOptions
CILocalStorageNotifier
CIPatch	The IPatch interface represents patches of the local storage. Each such patch somehow changes the layout of local storage persistence so that only compliant & corresponding versions of libquentier can be used to work with it
CLocalStorageOpenException	The LocalStorageOpenException is thrown on failure to open the local storage database
CLocalStorageOperationException	The LocalStorageOperationException is thrown when the local storage encounters some internal error during the attemt to process some operation
CNoteSearchQuery
Nsynchronization
Ntests
Nmocks
CMockIAuthenticator
CMockINoteStoreFactory
CMockISyncConflictResolver
CMockISyncStateStorage
CAuthenticationExpiredError
CIAuthenticationInfo	The IAuthenticationInfo interface represents the information obtained through OAuth and necessary to access Evernote API
CIAuthenticationInfoBuilder
CIAuthenticator
CIDownloadNotesStatus	The IDownloadNotesStatus interface presents information about the status of notes downloading process
CIDownloadResourcesStatus
CINoteStoreFactory
CISendStatus	The ISendStatus interface represents the information about the attempt to send information either from user's own account or from some linked notebook to Evernote
CISyncChunksDataCounters	The ISyncChunksDataCounters interface provides integer counters representing the current progress on processing the data from downloaded sync chunks
CISyncConflictResolver	The ISyncConflictResolver interface provides methods used to resolve conflicts between local and remote versions of the same data item
CConflictResolution	The ConflictResolution struct is a namespace inside which several other structs determining actual conflict resolutions
CUseTheirs	The UseTheirs conflict resolution means "override mine version with theirs version"
CUseMine	The UseMine conflict resolution means "override theirs version with mine version"
CIgnoreMine	The IgnoreMine conflict resolution means "use theirs version and ignore mine version as it doesn't really conflict with theirs version"
CMoveMine	The MoveMine conflict resolution means "before using theirs version change mine version as specified". Note: the data item inside this conflict resolution might refer to something different than mine version passed to the conflict resolution function. It can be that way because the actual conflict might be with another local data item instead of the passed one
CISyncEventsNotifier
CISynchronizer
CISyncOptions	Options for synchronization process
CISyncOptionsBuilder
CISyncResult
CISyncState	The ISyncState interface provides accessory methods to determine the sync state for the account
CISyncStateBuilder
CISyncStateStorage	The ISyncStateStorage interface represents the interface of a class which stores sync state for given accounts persistently and provides access to previously stores sync states
CIUserStoreFactory
CRateLimitReachedError
Nthreading
Ndetail
CResultTypeHelper
CResultTypeHelper< F, Arg, typename std::enable_if_t< !std::is_invocable_v< std::decay_t< F >, QFuture< Arg > > > >
CResultTypeHelper< F, Arg, typename std::enable_if_t< std::is_invocable_v< std::decay_t< F >, QFuture< Arg > > > >
CResultTypeHelper< F, void, typename std::enable_if_t< std::is_invocable_v< std::decay_t< F >, QFuture< void > > > >
CResultTypeHelper< F, void, typename std::enable_if_t< !std::is_invocable_v< std::decay_t< F >, QFuture< void > > > >
CTrackedTask
Nutility
Ncancelers
CAnyOfCanceler
CFutureCanceler
CICanceler	The ICanceler interface provides isCanceled method which can be used to check whether some processing can be skipped because it was canceled
CManualCanceler
Ntests
Nmocks
CMockIKeychainService
CApplicationSettings	Enhances the functionality of QSettings, in particular it simplifies the way of working with either application-wide or account-specific settings
CArrayCloser
CGroupCloser
CEventLoopWithExitStatus
CFileIOProcessorAsync	Wrapper under simple file IO operations, it is meant to be used for simple asynchronous IO
CFileSystemWatcher
CIEncryptor	The IEncryptor interface provides encryption and decryption functionality which is compatible with that used by Evernote service
CIKeychainService	The IKeychainService interface provides the ability to interact with the storage of sensitive data - read, write and delete it
CException	The IKeychainService::Exception class is the base class for exceptions returned inside QFutures from methods of IKeychainService
CLRUCache
CPrintable	Interface for Quentier's internal classes which should be able to write themselves into QTextStream and/or convert to QString
CQuentierApplication
CQuentierUndoCommand	Has the sole purpose of working around one quirky aspect of Qt's undo/redo framework: when you push QUndoCommand to QUndoStack, it calls "redo" method of that command. This class offers subclasses to implement their own methods for actual "undo" and "redo" commands while ignoring the attempts to "redo" anything if there were no previous "undo" call prior to that
CShortcutManager
CStringUtils
CSysInfo
CUidGenerator
CAccount	Encapsulates some details about the account: its name, whether it is local or synchronized to Evernote and for the latter case - some additional details like upload limit etc
CErrorString	Encapsulates two (or more) strings which are meant to contain translatable (base) and non-translatable (details) parts of the error description
CINoteEditorBackend
CInvalidArgument
CIQuentierException	Interface for exceptions specific to libquentier and applications based on it
CNoteEditor	Widget encapsulating all the functionality necessary for showing and editing notes
COperationCanceled
CResourceRecognitionIndexItem
CITextItem
CIObjectItem
CIShapeItem
CIBarcodeItem
CResourceRecognitionIndices
CResult
CRuntimeError
CSpellChecker
CQPromise