Re: web
Here, on Free Hosting? PHP on the server (and, of course, JavaScript in the browser) with some security restrictions.
Everywhere? Name it: PHP, Perl, Python, Java, JavaScript, Pascal/Delphi, variations on Basic (Visual Basic, VBScript, LotusScript, etc.), Lisp (Common Lisp, Racket, Arc, etc.), ML (OCaml and friends), ColdFusion -- the list goes on and on. And then there are the compiled languages, like the .NET family (which compiles to an assembly language for a virtual machine). On paid shared hosting plans here, you can use Perl, Python and ASP.NET (via Mono) in addition to PHP. Other hosts offer other language environments (some of which require a different web server, like Windows+IIS, IBM Lotus Domino, Adobe ColdFusion, Node.JS, etc.).
If you mean "what is a scripting language", it's generally a language you use to change what another program does rather than create your own programs. That can get a little bit fuzzy, since languages can be used both for scripting and for program creation, and some "scripts" (like the PHP you use to modify how a web server responds to requests, or a non-trivial Perl script on a Linux shell) occupy a territory that sits somewhere between a complicated macro and a fully-fledged program in its own right.
“Beware of bugs in the above code; I have only proved it correct, not tried it.” --Donald Knuth
"It was as if its architects were given a perfectly good hammer and gleefully replied, 'neat! With this hammer, we can build a tool that can pound in nails.'" -- Alex Papadimoulis (on TheDailyWTF.com)