Everything - and I mean everything in SL is created in world by the poeple in SL. Landscaping, textures, avatars, clothing, scripting, animation - you can do the lot!
Sl does have some bad points though - it can be exteemly laggy at times (especially if you have a poor internet connection or low bandwidth)
You also need a good graphics card - I use an NVidia 7600 GS, which works well. ATI cards do not.
Sometimes - Rarely you can lose items from inventory. Finaly because SL Client is constantly being updated some parts of sl do not work all the time.
I have a house, a harbour and a park, Built on what was quite literally a flat open space. The trees shed leaves and cast shadows, I have a stream with running water that splashes if you go into it. You can fish in it (And catch fish) . There is a Dance floor where you can choose from several dozen dances. I have a working motor boat in the harbour and a jet ski. I have a hammock you can lay in which swings + a load of other stuff including a horse that I ride.
I have working Weapons for RP too including a Sword, Knives, a Bow (Which I love) and a set of revolvers.
Leon - if you decide to take a look - once you are in world click on the 'Search' button at the bottom of the screen. then click on the 'People' tab at the top of the box. Type in 'Edwin Martinsyde' and click search. My profile should come up. You should then be able to IM me and I will add you to my friends list.
I am currently helping to launch a 6 sim rp area called Gianfar - this is based on the 'Dragons of Pern' books by Anne McCaffrey so I am having a lot of fun here atm

Launch is set for the 6th Sept so if you can get in befor that and come to the opening you will have a lot of fun I can promise you

If anyone else who knows me wishes to explore SL for a while please feel free to contact me once you have set up your account and logged in.