Maintenance is the minimum amount of working out that will maintain what you've gained during your competitive season /improvement cycle.

For example, if you accomplished your goal of benching 225lbs. for 5 reps, your maintenance program would ensure that you maintained the ability to do that. It usually takes 1/3 the amount or intensity of effort to keep your gains.

Pre season on the other hand is to prepare you for higher levels of training required to compete or improve some more. Ideally, a person will have some sort of goal in mind such as getting stronger, faster, leaner, etc.

After maintaining your previous cycle gains, you will then step up to a preseason training cycle that would be more intense than maintenance. This phase may last from 4-6 weeks depending on your level of fitness at the time. If your maintenance cycle has been truly minimal (little to no training) then a longer pre season cycle may be necessary. The reason for the pre season is to acclimate the body for higher more intense training ahead. Each phase or cycle is followed by a bit of off time. The rest may last from as little as 3 days to up to two weeks. Time off is also relative. For some people "time off" means absolute rest, only easy recreational activities. For others it just means going back to an easy maintenance type training. I recommend taking at least 2 days completely off between cycles, doing only easy walking or other low-impact, minimally stressful activities.
One can also gradually go from phase to phase in small increments. You could add weight, reps, sets, exercises, agility drills, etc. over a 4-6 week period so that you would end up at the beginning of pre season type training within relatively the same time frame.

The key is to determine what best fits your personality or time constraints. Also, if you feel tired, unmotivated, unusually sore or achy, take some time off. Those are good indicators that you may be over training. If you continue working out in a fatigued state you will soon be injured, ill, or both.

Pre season workouts may begin from 8-16 weeks before a competition Again it depends on how far away you are from competitive condition. For some body builders the diet season lasts from 12- 16 weeks. The point of this long phase is to strip the body of excess fat slowly so as not to lose muscle along with that fat. For other sports a shorter training phase is in order due to the tremendous wear and tear the athlete endures either during training or competition.