This is the comment statement of BASIC. Everything on the line is ignored by the interpreter. The line is not executable; it is merely skipped, but greatly aids the readability of the program.
The beginning of the program should have comments that name the author and purpose ot the program. The code should be commented whenever something unusual is done, so that the reader can follow it. Often the pseudo code statements used in design are included as comments to describe groups of BASIC statements that were one step in the original stepwise refinement process.