1999 Chevy Cavalier Idles slow

Engine Performance problem
1999 Chevy Cavalier 4 cyl Two Wheel Drive Automatic 110k miles

Hi Members,
I had my car checked and was told it was idling to slow about half of what its supposed to be.
What causes this and what do I need to fix this?Also
where on this car is this problem?Im new to this car bought it Saturday and already had to replace an
alternator and battery. So much for a used car grrrr.