sure, it's based on regular expressions, which is a way to see if a string value matches a pattern. In this case, the pattern is between the slashes. So /flex/ will match any string that contains "flex" which means it will match both "flex" and "-webkit-flex".

Regular expressions can get really complex, but they're also really powerful, so I recommend looking into them.

This code broken down is /patterntomatch/.test(stringtomatchagainst) and will return true if the pattern is found and false otherwise.