Simply:
Autolisp is used for making AutoCAD shortcuts and timesavers.

More complexly:
Lisp is a programming language that was developed in the 1950's. It's pretty powerful. I speak as on who has studied Basic, VB, C, C++, Batch programming, and a bits of others. In lisp, everything is a function... everything. Everything returns a value. Therefore, in theory, you can create a sentance that almost makes sense.
Ex.: (and (give 3) (take 2))
Assuming I've created the functions (give x) and (take x), that sentance would read, "Give 3 and take 2".

Because AutoCAD uses large lists to define its objects, it needed a language that handled lists - and deep ones at that. Is this better than C? No, but it's easier and the syntax is more consistant. AutoCAD wasn't built for hardcore programmers, but it wasn't built for beginners either. Lisp is middle of the road in regard to programming languages. Of those languages I know, it is perfect for AutoCAD. Lisp was a great choice.

Application:
What that means for you who use autocad is that you can do nearly anything the folks at autodesk can do... The only catch is, you have to work to make it happen. That's where I come in. I'm here to help. I love programming, but I don't want to be trapped into doing it 8 hours every day. That's what we call brain mush. I don't mind creating them on the side, though. I also like helping people learn.

I hope to be a help for you who wish to rest your weary hand of typing the same things over and over again. I wish to rest your weary brains of calculating the same math problem twenty times a day. I wish to speed your process. I wish to make your life easier. I don't want you to have to zoom in and out, measuring lines, circles, and creating layers. Please ask me. I'll try my best to turn your 450 key processes into 3. I'll turn 10 clicks into 1. Just ask if you need anything... and refer me to anyone else who might need my help.