We make agreements with each other all the time. Some of these are contracts but not all of them are.
We need contracts so we know what is agreed and what to expect.
A contract involves and offer made by an offeror. This is then accepted by an offeree.
There is often a written contract. However, sometimes there is no written document. A contract can be accepted by behaviour.
Social agreements are not contracts. If Gill agrees to meet Ram for a date and then stands him up this is not a contract. If Susan makes an agreement with Ulrika to go bowling together and then cancels on Ulrika there has been no contract. You cannot sue someone for failing to show up at a dinner party.