Cutting is essentially a phase where you lose the fat gained in a bulking phase, while minimizing muscle loss.
There are no hard and fast diet rules, but typically one would reduce daily caloric intake. This in itself is tricky. Most diets give some estimate of the number of calories to cut, but the bottom line is that the fat loss process varies from person to person. Check out the "T-Dawg" diets or for something more extreme, look into the "Velocity Diet". Again, these will provide some guidelines to start from, but nothing beats carfully tracking your caloric intake along with your fat loss progress.
You'll find lots of "conflicting" ideas about training during a cutting phase. Some advocate the inclusion of cardio. Others will say cardio is unnecessary for fat loss and will only burn muscle. Some will say drop the heavy weights and stick to lighter workouts. Others will tell you to stay heavy to minimize muslce loss. One thing you can probably count on is NOT setting any PRs due to the restricted caloric intake.
Again, experiment and figure out what works for you. That's half the fun...