The Big Crunch is a theory about the ultimate fate of the universe. This theory suggests that the universe will eventually stop expanding and will begin contracting, eventually collapsing in on itself in a massive explosion known as the Big Crunch.
The idea of the Big Crunch is based on the concept of cosmic inflation, which suggests that the expansion of the universe could be driven by a field of energy that is present throughout the universe. This field could eventually cause the universe to contract, leading to a collapse and a new Big Bang.
It's important to note that the Big Crunch is just a theory and that we do not yet have a definitive answer about the ultimate fate of the universe. Other theories, such as the Big Freeze and the Big Bounce, also propose different scenarios for the end of the universe.