The drag system on a reel is an often overlooked but very important part of your ability to catch a fish. It helps tire out the fish and helps keep your line from breaking off.
It's a sort of a clutch which is supposed to let the line unwind in a controlled manner off the reel when a fish (or anything else) pulls so hard that the line is in danger of breaking. There are many different drag arrangements on different kinds or brands of reels. They are all adjustable so you can control the amount of pull it takes to make the line peel off the spool but there is a wide variation from one reel to the next in how precise the adjustment can be and in how smoothly the line slips out. A drag which feeds line out smoothly is very valuable. When a fish suddenly strikes or
when an already hooked fish makes a sudden run you want the drag to immediately feed line with no jerks or catches. A sticky drag can cause a line to break in a hurry. Have you ever heard this fish story: "I got a strike so hard that my line was broken before I could do a thing?" We've heard it a lot and always think the same thing: If the drag on that reel was set right and working smoothly then the fish should never have been lost. The drag should feed line out so that the line never breaks.
There are several different drag set ups. Most involve a series of fiber and metal washers which spin against each other when the drag slips.
You'll need to service your drag system periodically to keep it functioning smoothly. Learn how to disassemble the set of washers so you can clean or replace them as necessary. Do this at least a couple of times per year or more, depending on how much you fish, more often if the drag starts to get sticky.
This is typical stack for a star drag reel. Also some spinning reels.