The middle star, also the uppermost, is known as Mizar. It has a companion Alcor which can be split by eye under good conditions. More detailed viewing will show a third star also in the same system. Stars also appear in clusters. There are two types - open and globular.
Open clusters contain very young stars.
The most famous are the Pleiades - or seven sisters. It is found in the constellation of Taurus and to the naked eye appears as six or seven fuzzy stars. Again detailed observations show more than these seven bright stars but in fact there are some two hundred stars. Also in Taurus is the Hyades cluster. This cluster is centered around Alderbaran the brightest star in the constellation.