Avatars are the software constructs which are used in the Metaverse. They are controled by a person, and the represent that person on the metaverse.
Avatar quality varies widely. The first difference is black and white vs. color. After that, resolution matters; higher is better. There is also the quality of rendering of the body and of the head. Realisticly rendered faces represent the top of the line in avatars.
There are very few limits on avatars. Two of the few rules are this: your avatar can not be taller than you are, and it can not be bigger around than you are. Many places in the metaverse have "avatar codes", and will not let people in who are using inaproapreate avatars.
These are avatars that you don't choose, you use. They are the avatars you get when you log into the Metaverse via public terminal, for example.
Using such an avatar can tel someone who knows about the metaverse a lot about how the person is accessing the metaverse. Such a person could tell how you were accessing the Metaverse, and even a little about where in the real world you were.
This is a grainy, black and white avatar, used by people who are accessing the metaverse via the cheapest public terminals.
The next step up in Avatars is a prepackaged one. You get to choose your Avatar, and it is of higher quality. But, you have a "limited" choise of several hundred commercial avatars, and a couple of thousand "shareware" ones.
Below are a couple of the most popular and most representitive:
The toys from the last century.
This avatar looks like the pilbury doughboy. It is made out of easy to render polygons, which is kind of nerdy. It is, however fast and higher rez than other avatars in the same price/computation range.
He lives, as an avatar.
The next step up from a purchased Avatar is one made from a commercially available kit. Any skilled person could do that, but typcially a programmer would be hired to do this work. Typically, there is lots of appearance controls, and a little control over capabilities and resource allocation.
This popular series of kits can be used to create most media starts from the last 50 years. There are five kits in the series: teenage women, teenage men, young women, young men, and mature men. (There are not enough mature women media starts to make a kit. :-)
Many people want an avatar which looks like they look in real life. This kit provides many pieces of a human body, with many skin tones, and lots of clothing to put over it.
The high end avatar is a custom one, created to a personal desire. There is no limit to the creativity here, except for money and time.
Rules covering avatars are enforced by the software which implements the metaverse. You just can't beat it, without having inside knowledge of the metaverse. Rules on avatars cover specific parts of the metaverse, not the whole thing. Private parts of the metaverse can have any rules, or no rules.
Public areas generally have two rules: your avatar can not be taller than you are, and your avatar can not be bigger around than you are. There are also "speed limits" of sorts, which keep avatars moving only slightly faster than realistic.