Well, generally it means that the deadlines in the contract to do (or not do) something must be adhered to. If you don’t meet those deadlines, you have breached the contract and penalties apply. What kind of penalties? That’s a different post.
But what if the contract doesn’t have any specific deadlines? This is when it gets tricky. Now it depends on what the contract is about? Buying or Selling a home? Obtaining a loan? Making a delivery? Each specific fact will affect the decision. One thing that will affect the decision is whether or not a good faith effort has been made to meet the deadline you agreed to.
Seem confusing? You are correct. It can be hard to tell.