A brain address is a pointer to a well-defined location in a well-defined brain atlas.
The location part can be as simple as an x,y,z-coordinate or brain region acronym.
The brain atlas part can be as simple as the combination of two acronyms:
that of the brain atlas provider, and that of the atlas that the provider hosts.
For example, the address
brainaddress:sba/ABA_v3?coord=1,2,3
points to coordinate (1,2,3) in atlas ABA_v3 hosted by provider sba.
Further explanation and specification of the brain addressing system can be found at https://brainaddress.org.