Different commands allow you to list, copy, rename or erase data within the current location..
g.list: Lists available GRASS data base files of the user-specified data type to standard output.
g.rename: Renames data base element files in the user's current mapset.
g.copy: Copies available data files in the user's current mapset search path and location to the appropriate element directories under the user's current mapset.
g.remove: Removes data base element files from the user's current mapset.
If you wish to deal with an entire location you will have to do so by hand, after having left GRASS.
In order to remove a location with the name "location_name", go to the directory that contains this location (i.e. the GRASS database directory) and use the command rm -rf location_name. This will irrevocably erase all the data, so be careful !
In order to copy a location with the name "location_name" to another directory or another machine, go to the GRASS database directory and use the command tar cvf location_name.tar location_name to package the entire directory into one file. You should then compress this file with gzip location_name.tar or bzip2 location_name.tar. Copy the resulting file to the new location. Be aware, however that user and group settings (gid and uid) might get mangled, so be prepared to change those with chown.
In order to access maps within the same location, but in another mapset, you have to set your mapset search path. If you do not wish some of your data to be accessible for everyone, you can limit the access to a particular mapset you own.