You will have a binding contract if the seller, upon receiving your written offer, signs an acceptance just as it stands, unconditionally. The offer becomes a firm contract as soon as you are notified of acceptance. If the offer is rejected, that's that - the sellers could not later change their minds and hold you to it.
If the seller likes everything except the sale price, or the proposed closing date, or the basement pool table you want left with the property, you may receive a written counteroffer including the changes the seller prefers. You are then free to accept it, reject it or even make your own counteroffer. For example, "We accept the counteroffer with the higher price, except that we still insist on having the pool table."
Each time either party makes any change in the terms, the other side is free to accept, reject or counter again. The document becomes a binding contract only when one party finally signs an unconditional acceptance of the other side's proposal.