A suit for specific performance is like an court injunction, ordering one party to complete the performance promised in a contract. Because most contract issues can be resolved by money damages (in a lawsuit), an equitable suit for specific performance usually only arises with unique property; real estate is unique. Some jurisdictions still have separate courts of chancery for this type of complaint.
In theory, if you have a written contract to buy some real estate and you perform all of your obligations (offer to pay), you can "force" the completion of the sale, using specific performance, if the seller refuses to go through with it. On the other hand, a court is unlikely to order you to purchase the land (if you're the one who refuses to go forward with the contract) because the law of equity prefers the status quo, and the seller could be made whole by simply collecting money damages from you for their trouble.