Answer:
This answer depends on what language you're using, but in most languages, "//" is used to precede a one-line remark. "/" is used to divide a number by the other. For example:
// this is a remark
var foo = x / y;
There are exceptions to both, although the / is almost universally used for division. One exception would be assembly of course, I don't know if there are any higher level languages that don't use the slash.
