There are a few things to factor in when buying a telescope. One, what is your budget.Two, what are your intentions with it. Three, what kind of portability do you want. This is not a complete list but you get the point.
First, you have to decide how much money you are willing to spend. You can get a dobsonian telescope for around $300.00 and the bigger the scope the more you will spend.
You can get a Schmidt cassegrain telescope for about $3000.00. So prices really vary a lot.
Now how portable do you want it to be. A dobsonian telescope can be very big and very bulky. Where as a refractor telescope is very portable.
Here I have included links to photos of different telescopes. Here is a dobsonian telescope http://upload.wikimedia.org/wikipedia/commons/thumb/f/f5/Dobson-mount.jpg/180px-Dobson-mount.jpg Here is a Schmidt cassegrain telescope http://www.skiesunlimited.net/images/products/527_01.jpg Here is a standard refractor telescope http://us.st12.yimg.com/us.st.yimg.com/I/opticsplanet_2044_1016750428. If you've looked at the photos you can really see the difference.