You have three options for pass coverage: Man-to-Man, Two-Deep Zone, and Three-Deep Zone. Each has strong and weak points.
Man coverage requires very capable linebackers and defensive backs. If you want to doubleteam or blitz, you have to be in Man coverage. Also, Man coverage isn’t quite as susceptible to playaction fakes and draws. In Man-to-Man, defenders cover their men closely, and it’s the best coverage against short passes. However, it can be risky against long passes.
Two-Deep Zones, also known as “Short Zones” and “Halves.” With two deep and five short zones, this coverage can be very tough on medium passes, especially the 10-12 yard routes. It’s also good against long passes and a little better against most runs, but is more vulnerable to draws. It’s also open to crossing passes to the tight end, who splits the two safeties.
Three-Deep Zones, also known as “Deep Zones” and “Thirds.” The deep part of the field is broken into thirds, along with four short zones. This is the best coverage against long passes, and is still good against medium passes, especially the 14+ yard routes. It is more vulnerable to short passes and a little more vulnerable than two-deep versus the 10-12 yard medium passing routes.