Improved wording

PBF is based on Google Protobuf. But saying here that it is a Google Format is misleading.

Author: joto

en/basemaps/install.txt

@@ -83,7 +83,7 @@ Source: http://imposm.org/docs/imposm/latest/tutorial.html#writing
    $ sudo -u postgres psql -d osm -c "GRANT ALL ON ALL TABLES IN SCHEMA public TO \"www-data\";"
 
 Let's explain this better: First we download 2 pbf files from Geofabrik
-OpenStreetMap data. PBF is just another format well compressed from Google.
+OpenStreetMap data. PBF is a space-efficient binary format used for OpenStreetMap data.
 *pwd* and *ls -1* commands are just there to show you where we are and what we
 get.