If we didn’t close down the pools the water would freeze in the pipes and burst (it’d be way too expensive to keep the pool running all year because the heater would have to be on to avoid freezing) - so we reduce the water beneath the scimmer so no water can enter the pipes/pump/filter. But this is because our winter is…well, winter. You’re probably okay with running it every so often to the water does sit and freeze where we would have an issue.
We blow the lines (reverse vacuum) so all of the water is out and then plug them, this means the filter and pump are also empty. Come summer, we fill the pools/all the lines again. We would then throw a tarp over the pool to prevent water, leaves, etc from going into the pool.