Generally speaking, APRS data in the RF environment is very short-lived.
Once gateways between local RF APRS activity and the internet APRS-IS
were invented, interest arose in storing APRS data for later review. By storing the APRS packet data
in a database things like tracking become more interesting.
Any internet user can do a search of the database to look at station position reports,
messages, any data that made it’s way into the APRS-IS system.
Probably the best known APRS database is findu.
This aspect of APRS has become overwhelmingly popular. People set up their
station PATH so that their packets reach an I-Gate and make it into
the findu database. This use has in many ways overshadowed the original purpose of APRS
as a local, tactical, RF-based tool.
A byproduct of the whole database and APRS-IS thing is that
APRS Station identifiers have to become more globally unique.