need information about storing methods

Hi,
I'm nowadays tryng to use postgresql to store geographical data to use
them with a gis program (GRASS).
The coordinates of each point are stored in a field that is a
point-type.
Anyone can tell me if postgress uses, for this kind of data, a storing
method like HHCODE, poin-quad-trees (or anything better) , or it stores
point-data like anything else?
A query like this one:
" SELECT coordinates FROM table WHERE coordinates @ '((1,1),1)'::circle
"
is executed like anything else, processing evry tuple in the table ?
If so, anyone knows how to implement a more complex storing method?

Thanks to all,
Christian Saldarini