Typically a property for sale will go from Active, to Active Contingent (or Subject to Inspection), to Pending, and finally to Sold.

Active means a house is currently for sale - you can make an offer.
Back on Market
Contingent means the property is Active, but the offer is contingent on selling another home. You can bid on this home if you want to but the first buyer will have the option of waiving the contingency clause and keeping their deal.
Backup Offer means that the house is Contingent, but that the seller is taking additional offers (you can make an offer on the property).
Subject to Inspection means an offer has been made on a house, but it is contingent on a satisfactory inspection.
Pending means that the purchase contract has been fulfilled and the closing of the transaction is essentially assured (you can keep your eye on it to see if it completes).
Price Change
First Right Of Refusal means another buyer has the right to match your offer before the seller sells.
Sold means the house sold! We show sold listings with photos wherever we can.