It is an existence for moving freely in virtual spaces as another self.
It is possible to set a face, hairs etc. favorit appearances.
Using expressions and gestures helps communications to other users.

Some services can also import original avatars of users other than avatars which are provided from each services.
This is useful if provided avatars are not satisfiable or if the same avatar is wanted to use in several services.

As main 3D data types, there are FBX type and VRM type.
FBX type is a standard 3D file type while VRM type is a type specialized for the humanoid avatars.
The VRM is a type from Japan, so it is mainly available for services in Japan domestic, but in the world, the FBX is mainstream.

Tools able to create 3D data are needed. Blender and Maya are general.
Especially as Blender can use for free, it is a very thankful tool for creators.
There is also VRoid Studio specialized for avatar creation of the VRM type.

Currently it is different handling in every service, while for the future, it may be normal that each self avatars are brought like SNS icons.
For myself, the appearance of avatar is not at all careful, but I wonder that why people worry only someone's else eyes even in virtual spaces.
At this time, this is an enumeration of informations researched using internet yet, from next time, variously practical something will be tried.