There are two types of reports: Opening and Player Reports.
Scid's
Some features are affected by the "Maximum games for statistics" Option, which is 10,000 by default but can be increased to 100,000. The default Theory Table Games is 500 (and 10,000 maximum).
The first few sections show matching games and subsequent moves. One can see if the opening is becoming more popular, if it has many short draws, and what move orders (transpositions) are used to reach it.
Section 4, Moves and Themes, reports the move orders leading to the position, and also positional themes within the first 20 moves. To be counted , a game must match a theme in at least 4 positions of its first 20 moves. This avoids the brief occurrence of a theme (such as an isolated Queen pawn which is quickly captured) distorting results.
The final and largest part of the report is the Theory Table. When saving the report to a file, you can choose to save just the table, a compact report without the table, or the whole report. The hyper-links (in red) reference diverging games.
The Theory Table has a game limit of 500 by default (but configurable in Report Options). If the report position occurs more often, only games with the highest average Elo are used to generate the Theory Table.
Clicking on the board will flip it. Right-clicking will resize it. Most coloured items in the report window are clickable, and invoke some relevant action. For example - clicking a game reference will load that game, or clicking a positional theme will set the filter to matching games.
Merge Games merges the 50 best games from the Opening Report into the current game as variations, including full references.
Exclude allows removal of a move from the Theory Table.
Almost all the report sections can be turned on or off or adjusted in the Opening Report Options.
The Favorites Menu in the Report Window allows one to maintain a collection of favorite opening positions.
Add Report adds the current position as a favourite, and Generate Reports generates a report for each of these favorites. A dialog-box will appear allowing you to specify the report type and format, and a directory where report files will be saved. A suitable suffix for the format you selected (e.g. ".html" for HTML format) will be added to each report file name.
Player Reports are similar to Opening Reports, but
contain information about the games of a single player with the White or
Black pieces. One can generate a Player Report from
Player Reports can be generated for all games (with the specified player and pieces), or for games matching the current position.