A plunger is something that no household should be without. It is one of those items that you really don't think about until you need it. When you need it you normally do not want to take the time to run to the store and pick one up.
Plungers are simple looking devices that have a rubber cup on the end of a handle. The curved rubber cup when pressed down will force air into a drain. The air being forced into the drain will push whatever is clogging the drain on down. They actually work great for such simple products.
A plunger can be used on most drains including toilets, bathtubs, and sinks. There are a couple things to consider when using a plunger. When doing the actual plunging there needs to be a good seal between the rubber of the plunger and the area surrounding the drain. If there is not a good seal all of the air will not be forced into the drain, which will diminish the effectiveness. The other thing that I like to do is to have one plunger that is used for toilets and another for everything else. This isn't a requirement but it seems more sanitary to me.
Using a plunger is pretty easy. It doesn't take much in the way of technical knowhow. Some clogs are just too much for a plunger and this is where things like drain cleaner, a plumber's snake, and actual plumbers need to be considered. If a couple of attempts with a plunger doesn't work just go on to the next possible solution. Plunging for an hour is good exercise and will work up a sweat, but it won't get the toilet working again.
Basic plumbing supplies should be kept in all houses for simple to fix emergencies. Every household will at one time or another will have a clogged drain, and having what you need prior to the emergency will save a lot of stress and aggravation.