Serious answer, it does very much vary depending on the organisation, so while you may get some ideas from advertised roles, chances are they'll still need a bit of tweaking (e.g. there's no point copying a job spec. for a 2nd line technician that requires Windows experience when you have a purely Linux or Mac environment!). Also depends a lot on the size of the organisation - when I was a "1st/2nd line technician" for a college, I was doing basically everything from replacing toner in printers, to configuring Cisco switches and patching up phone connections, whereas if you worked for a bigger company, you'd most likely find yourself pigeon-holed a lot more, i.e. 1st line would literally just be answering phones and only dealing with the most basic of queries while having to pass anything more "interesting" up the chain.
Generally speaking though:
1st line - deal directly with the customer, check the basics (is it plugged in, have you tried a reboot, etc.) and filter out "time wasting" calls. Probably will have a knowledge-base to refer to and so wont have to do any real thinking or problem solving themselves. Generally the same thing day in day out.
2nd line - deal with any issues that first line haven't been able to solve (either due to lack of expertise/skills, or because it's not within their remit. Day to day again can be very samey, although you may get the occasional more interesting/challenging problem.
3rd line - deal with the "behind the scenes" stuff, like infrastructure, server config/admin etc. Any major issues, projects, also things like maintenance, network monitoring, security etc.