Try the underside of the cover, there is a legend which tells you what it is.. will look at it when I get back to my car later for more precise identification.
Relay, Various Applications, (Orange), 318i/is/iC (1992-98), 318ti (1995-99), 325i/is/iC (1992-95), 328i/is/iC (1996-99), M3 (1995-99)
Relay for Motronic, 5-Prong (White), 318i/is/iC (1992-98), 318ti (1995-99), 325i/is/iC (1992-95), 328i/is/iC (1996-99), M3 (1995-99)
Last Could Be:
1.)Changer Relay for Cars with Emission Control Air Pump, 318i/is/iC (1992-98), 318ti (1995-99), 323i/is/iC (1996-99), 328i/is/iC (1996-99), M3 (1995-99)
2.)Diode Relay for Auxiliary Fan 5-Prong, 318i/is/iC (thru 05/92), 325i/is/iC (thru 05/92)
3.)Comfort Relay (Closing/Contact Relay), 318i/is/iC (1992-98), 318ti (1995-99), 323i/is/iC (1996-99), 325i/is/iC (1992-95), 328i/is/iC (1996-99), M3 (1995-99)
But if all else fails there is an easy test to find out what it does...
Pull it out and find out what stops working.