A maintenance contract is used for reoccurring jobs that happen over the course of a season. A service ticket, on the other hand, is for a quick job that will take less than a day - a repair, a follow-up visit, etc.
You want to use a service ticket when you have a job that you're only doing once and which won't take very long - maybe you need to fix a rut in a yard, replace a pump, find a leak in a water feature... you get the idea.
When you go to schedule a service ticket, you drag and drop it onto the Calendar, assign it to a foreman, and enter the amount of time you think it will take - whether 30 minutes, an hour, all day, etc.
You want to use a maintenance contract when you do the same type of job for the same customer repeatedly - maybe it's lawn mowing, landscape maintenance, or water feature maintenance.
When you go to schedule a Maintenance Contract, you schedule all the jobs for the whole season at once, whether it's weekly, twice a month, etc.
Those are the basic differences between a Service Ticket and a Maintenance Contract.
Let me know if you have any questions!