The Pyraminx was invented by Uwe Meffert of Meffert's Puzzles in the early 1970s. There are 4 triangular faces made up of 9 smaller triangles. The tips can be rotated by themselves or with the 3 connected triangles.
Pyraminxes are nice puzzles but about the easiest thing in the world to solve - not always a bad thing if you are strugglling with following the solution to the cube. Most people tend to stumble over the method if they spend a little while having a go on a pyraminx. If you memorise your method and have a few goes, you'll soon be doing this in about 20-30 seconds.
The pyraminxes that you buy from Meffert's site are reasonably good quality and tend to last well if looked after. A second hand one may need a clean-up and some puzzle lube but will still be fairly good. There are some fairly low quality knock-off ones for sale, so take care if you buy a pyraminx.