What is the difference?

What is the difference between an offer to purchase agreement and a option to purchase agreement?

The offer to purchase states you are going to purchase the property the option to purchase states that you have the OPTION to purchase but not the obligation.

what Mr Investor said… in simpler terms:

Purchase Agreement is a contract to buy where both the seller and buyer are committed to do the sale.

Option Agreement is where the seller commits to sell the property to the buyer, but the buyer can choose not to. Commonly used with leases where someone may lease the house and buy an option to buy it at future date. He may not execute his right and just not buy (losing his option money).