Most All Sand Filters are the same. They mostly all have what is called a multi-port valve on the top or on the side. So lets say you are looking at your sand filter multi-port valve right now. You should have about 6 settings including:
Filter Backwash Re-circulate Winter/Closed Rinse Waste
If you don't have these exact setting you probably have something similar and these are what they do
Filter Runs pool water from your pump through the sand filter and back into the pool. You will use this setting about 90% of the time. This is your main setting
Backwash Runs pool water from your pump through the sand filter and out through the waste port dispensing water out of your pool. This is what cleans your dirty sand. You should only backwash when your pressure rises 10 pounds over your normal pressure rate.
Re-circulate Runs pool water from your pump into your multi-port valve and into your pool never touching the sand. This just spins the water around. Some chemicals require you to do this like floc. Rarely used.
Winter/Closed This setting closes all the ports in your multi-port valve for closing your pool or stopping water from going through the multi-port valve.
Rinse Runs pool water from your pump through the sand filter and out through the waste port rinsing the sand clear of dirt. You should always rinse your filter after backwashing ensuring no dirt flies back into your pool after backwashing.
Waste Runs Pool water from your pump through your multi-port valve and out through the waste port never touching the sand. You will use this setting if you are manually vacuuming your pool and the dirt keeps flying back in through the return line. This means that the filter can not filter that much debris at one time so you will have to not use the filter and just suck the debris right out of your pool causing you to lose water. This is very effective at cleaning a large amount of debris.
Note: Any time you move the handle on your multi-port valve to switch positions or settings you must first turn off your pump. Keeping the pump running while moving that handle can cause you to blow the gasket in your valve. Not an expensive fix, but a fix you can avoid.