These avatars are made of mesh and I am not sure how they work but they make you very very tiny (the size of your boot). They come in all shapes and forms but you need to read everything carefully because they need special clothing and accessories although I found that normal AO's and dance chims/huds work with them just fine.
Can you imagine if everybody became a petite? Your small plot of land could instantly become the size of 20 sims. Tier would shrink overnight as tiny avatars downsized their land hahahaha.
You can find assorted petites around the grid but best places I have seen so far is FALLEN GODS and PETITE AVATAR KINGDOM which has free demo's to try before you decide if you love it or not. You must have a mesh enabled viewer or you will not look right.
I may stay a petite for the foreseeable future so if you see me around say "hey" but just don't tread on me!!!!!