Polish is a Western Slavonic language with about 40 million speakers in Poland, Lithuania and Belarus. There are also fairly large communities of Polish émigrés in the UK, USA, Canda, Ireland and Brazil. Polish is closely related to Kashubian, Lower Sorbian, Upper Sorbian, Czech and Slovak.
Polish first appeared in writing in 1136 in the 'Gniezno papal bull' (Bulla gnieźnieńska), which included 410 Polish names. The first written Polish sentence was day ut ia pobrusa a ti poziwai (I'll grind [the corn] in the quern and you'll rest), which appeared in Ksiega henrykowska in 1270. In Modern Polish spelling that sentence is daj ać ja pobruszę, a ty poczywaj.
The native name for Polish is polski (Polish), język polski (the Polish language), or more formally, polszczyzna (Polish).