In many stores entry and exit are indicated to get people to pay orderly.
Usually this happens in shops where there are usually many people buying the same time, and in some services, for example in transport ticketing and information points.
Although sometimes it is written in English, it is important to learn these simple kanji entrance 入口 and exit 出口because we can read in many places.
This way of proceeding is a clear example of the order that has the Japanese society. This way ordered to pay is very good, because in this way is difficult for someone to leak.