The help files for the commands will point these out. Other commands assume no default values, and the user will be required to provide a keyword on the command line. Several commands may be placed on a single line, separated by semicolons. GO Which executes each of these 4 commands in order, as if you typed them one at a time. See the section on procedure scripts below for details.
Most words turn on or off options in the programs.
In this case, the parser treats everything between the 's as a single string. These are combinations of keywords and arithmetic constants, and are used to pass values to Prospero subroutines,where needed. This is because the Prospero command parser treats space characters to separate keywords on the command line. Putting in extraneous spaces would confuse the parser into thinking each element was a separate keyword, invariably generating an error.