SCID works with its own file formats and other standards. Here's the complete list of file types, ordered by their extension:
A fin containing an engine book in PolyGlot format - v. [TheBookWindow].
A file containing various configuration settings - [HowToConfigureSCID] or [TheOptionsMenu].
A file containing the ECO codes to classify the games in a database - v. [TheMaintenanceWindow] and [TheECObrowser].
A file containing Nalimov tablebases - v. [TheTablebaseWindow].
A file containing a collection of positions in Extended Position Description (EPD) - v. [HowToUseEPDfiles].
A file containing a collection of positions in FEN, i.e. the Forsyth–Edwards Notation.
A file in Portable Game Notation, a popular standard for exchanging chess games - v. [ThePgnWindow].
A file containing your opponents' emails when you play Correspondence Chess - v. [TheCorrespondenceWindow].
A file containing your repertoire masks when you open a SCID base in Tree mode - v. [TheTreeWindow].
The three files of a [ScidDatabase].
A file containing SCID header or material/pattern search settings - v. [HowToSearchDatabases].
Files containing spellings, ratings, and players photos - v. [HowToShowPlayersPhotos].
The various files that create the GUI of SCID in TCL - v. [HowToTweakScidInterface].
Wiki: HowToConfigureSCID
Wiki: HowToSearchDatabases
Wiki: HowToShowPlayersPhotos
Wiki: HowToUseEPDfiles
Wiki: ScidDatabase
Wiki: TheBookWindow
Wiki: TheCorrespondenceWindow
Wiki: TheECObrowser
Wiki: TheMaintenanceWindow
Wiki: TheOptionsMenu
Wiki: ThePgnWindow
Wiki: TheTablebaseWindow
Wiki: TheTreeWindow