If it only has and on/off switch...mode A only (code but no altitude)
Switch with on/off/alt..........mode C (code and altitude)
Switch with on/off/alt/
ID (or FLIGHT ID) Mode S...
which means it also has a data link capability.
With the right equipment you can receive traffic info from ATC like with a TIS system:
http://www.aopa.org/whatsnew/air_traffic/tis.html