In all cases, text in brackets ([]) is optional, although the brackets themselves never appear in the actual command. For example, the command -str[ings] pool can mean either:
-strings pool
or
-str pool
Where an option has several possible permutations, the possibilities are separated by the pipe (|) character. For example:
-sym on|off|full|fullpath
means the -sym command can be followed by one or more of the following options: on, off, full, or fullpath. If you have more than one option, separate each option with a comma. So you might have -sym on, -sym off, -sym full, or -sym on, fullpath.
The plus sign (+) means that the parameter to an option must not be separated from the option name by a space. For example,
-D+name[=value]
means that you can have -DVAR or -DVAR=3, but not -D VAR.
In cases where you provide a variable parameter such as a file name, that item is in italic text. For example, -precompile filename means you must provide a file name. The help text that corresponds to the compiler option explains what you must provide.