Modern Jive is usually danced to music with a 4/4 time signature - nearly all pop music has this time signature and is also known as common time.
There are 4 beats to bar and at the fundamental level we step on each beat. As we get more advanced we can change the footwork so long as we are aware of the underlying timing. There are usally 4 bars in a phrase - see the Music Glossary for basic definitions of these terms.