You have an offer, Now what?

In the state of Virginia when purchasing a home or selling a home, you will have a legal binding contract when the seller and the buyer both sign the agreement. 

The offer becomes a ratified agreement as soon as you are notified of acceptance. If the offer is rejected, that is that and the sellers cannot change their mind.
If the seller likes everything, except let's say, the sales price, or the proposed closing date, or the hot tub that the buyers want to convey with the property, the sellers may offer a counter offer, with the changes the seller would prefer. 
Buyers are then free to accept or counter offer.  For example, "We accept the counter with offer with a higher price, except that we still want the hot tub."
Each time either party makes any changes to the offer the other side is free to accept or reject it or counter again.  The document becomes a legal binding contract only when one party finally signs an unconditional acceptance of the others proposal.  For clarification there is no attorney review in the state of Virginia as there is in some states.