TWiki Variables are names that are enclosed in percent signs % that are expanded on the fly. Some variables take arguments, such as %INCLUDE%. For those variables, the arguments are included in curly braces ({ and }).
The attachment URL of the current topic. Example usage: If you attach a file to a topic you can refer to it as %ATTACHURL%/image.gif to show the URL of the file or the image in your text.
Inline search showing the search result embedded in a topic. FormattedSearch gives you control over formatting, useful for creating web-based applications.
TWikiPreferences defines some site-wide variables. Among them are:
Line break: Write %BR% to start a new line.
Colored text: Write: %RED% Red %ENDCOLOR% and %BLUE% blue %ENDCOLOR% colors to get: Red and blue colors.
There are many more variables. To see them all, go to TWikiVariables.
Documentation Graphics: There are many graphics available to use in your topics. Use %ICON{"help"}%, %ICON{"tip"}%, and %ICON{"warning"}% to get: , , and , respectively. TWikiDocGraphics lists them all.
To "escape" a variable, prefix it with an exclamation mark. Write: !%SOMEVARIABLE% to get: %SOMEVARIABLE%.