Arcturus is Alpha Bootis, apparent magnitude -0.05, at 37 light years, spectral type K1.5 III, an orange giant, and the brightest star in the northern celestial hemisphere.
Two things distinguish it. The first is its proper motion, which is among the largest of any bright star: Arcturus is moving across the sky fast enough that its position has shifted noticeably since antiquity. Edmond Halley used exactly this, in 1718, comparing contemporary positions of Arcturus, Sirius and Aldebaran with those in Ptolemy's catalogue, to establish that the fixed stars are not fixed. That was the discovery of proper motion, and Arcturus was one of the three stars that yielded it.
The second follows from the first. Arcturus belongs to the Milky Way's halo rather than to the disc where the Sun and most bright stars lie. It is metal-poor and old, moving at high velocity relative to the local population, and is generally thought to be part of a stream of stars acquired from a dwarf galaxy absorbed by our own. It is a visitor, passing through the solar neighbourhood, and it will not stay.
The name is Greek, Arktouros, guardian of the bear, from its position behind Ursa Major, which the constellation figure of Bootes, the herdsman or ploughman, follows around the pole. It is one of the very few stars named in Homer and in the Book of Job, and its heliacal rising was a seasonal marker in Hesiod's Works and Days.
Arcturus is easy to find: follow the curve of the Plough's handle outward, and the first bright star on that arc is Arcturus. Continue the arc and it reaches Spica. The mnemonic, arc to Arcturus, spike to Spica, is the standard way of orienting oneself in the northern spring sky.
Sources AstronomyAndrew Fraknoi, David Morrison, and Sidney C. Wolff (OpenStax) with Almagest (Mathematike Syntaxis)Claudius Ptolemy