Hi I'm looking at buying a home and the MLS listing Status was at A this morning and changed to B. I found a definition of the codes:

BACK-UP OFFERS ARE BEING TAKEN. The seller/lessor is soliciting
Back-up offer(s) through the MLS. The seller/lessor has accepted a contingent
Offer. A second offer would be a back-up offer and would become the accepted
Offer only if and when the first agreement is cancelled.

What does this mean exactly??