A template is a series of steps that describe how to carry out a particular process. It's the blueprint that can be reused every time you need to do that activity.
A task is the name we give to the checklist that is created when you want to perform a process on a specific occasion.
For instance, you may have a template for recruitment which includes the basic steps such as writing job descriptions, sending out adverts and interviewing candidates.
The task would be the specific occasion you are recruiting for a role, for example for a Receptionist. The task is where the action of checking boxes takes place.
The task can also be made specific to the type of job you are recruiting for - steps may be added, taken away or amended depending on the requirements for that particular job.