Cars are horribly complex objects, made up of thousands of components and dozens of different systems, which all have to work with each other for tens of thousands of miles.
Sometimes things don’t go to plan and bits wear prematurely or stop working together, and that can often be safety critical. When things get to this point the car maker will usually issue a recall to put things right; all of the cars affected will be inspected and modified, so the whole thing doesn’t go up in smoke.
Most models of car are recalled at some point or other
The work is done by an official dealer for the manufacturer in question, and it'll be done at the manuafcturer's expense, so it won't cost you anything at all. Most models of car are recalled at some point or other; over time, some can be subject to several recalls while others may not need any at all.
The manufacturer will do its best to trace owners, but some slip through the net; if you’re in doubt about your own car, you can see what recalls it’s been subject to by checking out the Vehicle Inspectorate website. If you think your car may need recall work doing, contact your local dealer and ask them; their records should tell you whether or not any necessary work has been done.