What are Bases? 

Basically, bases are the foundation or mannequin type figure drawn by an artist, usually for personal or for other artists use. These bases are usually shaded in various skin tones, come without clothing or hair and are usually editable however, always seek the basemakers terms of usage to make sure.  Bases come this way so "dolling" artists may create their own art on them.
The face is usually drawn for you however, blank faces are sometimes provided should an artist prefer to draw their own.  There are male and female bases, usually without detail.  Think of them like a paper doll in which you can make your own digital clothes.

Please also see dolls defined by Wikipedia below.
Dolls (dollz) Definition

Dolling Terminology (under construction)

Drag-n- drop-  These are dollmaker sites. They come with ready made bases, clothes/accesories and hair to dress up.

Frankendolling- The taking of someone else's finished dolls/bases,  using the parts to construct a new doll/base and calling it your own. This is illegal.
 
Netiquette-  Or etiquette are guidelines doll artists follow normally including copyright, terms of use, social interaction during chat, visiting sites and forums. 

Terms of Use - These are the artists rules for using their work.

Adopting-  Adopting refers to displaying another artists doll(s)/pixel graphics on your website.  Following the artists terms of use should be observed closely before adopting due to linking requirements and copyright law.

Tutorials- These are instructions on specific categories taught by the artist. Usually short in length, with images provided for easy learning of their technique.

Base Edit-  Refers to the extent on how editable the base is. Some dollers allow full edits, a small percentage like myself do not. There are base edit contests. Always pay attention to their terms of base editing otherwise you are violating copyright.