A shower is where a person cleans themself by using water. They stand up when they use a shower and usually do not wear clothes in a shower. Showers have a shower head that squirts out water usually from above.
There are different kinds of showers. One is a "power shower" where there are many jets of water from all around. Another is the one in the picture. Some are in baths, and others are on their own.
Showers are mainly used for hygiene.