Polish is spoken by about 43 million people, 36.5 million of whom live in Poland, where it is the official language. After the end of Word War II, following border readjustments, Poland became more linguistically and ethnically homogeneous; over 98% of the population spoke Polish. Another 2.5 million Polish speakers live in the USA; 1 million in Ukraine; about 100,000 or so each in the Czech Republic, Slovakia, Germany, Israel, and Canada; and lesser numbers in Australia and Romania.
Polish is a Slavic--or Slavonic--language, and it belongs to the West Slavic subgroup. This subgroup also includes Czech, Slovak, Cassubian (or Kashubian, spoken in the Baltic coast region in northern Poland), Sorbian (Saxony and Brandenburg, Germany), and Polabian, which is now extinct.
Polish uses a Latin-based alphabet, which was introduced along with Christianity in the tenth century. It uses numerous diagraphs, as well as diacritics on certain consonants and vowels. Some variation exists in the spelling of some sounds. The Polish language also borrows extensively from German and Yiddish, and slightly from East Slavic languages. Other languages that have contributed lexis include Latin, Czech, Lithuanian, French, and Italian.
In the fourteenth century, entire texts began to appear in Polish, with the earliest being religious in nature. For example, this included a collection of sermons and a translation of the Psalms.
The sixteenth century--the Golden Age of Polish literature--saw the first printings of dictionaries, grammar guides, and spelling guides. Poland was first partitioned in 1772, and with this event, its language entered a crisis period as various occupying powers, primarily Germany and Russia, attempted to replace Polish with their own languages.
Source: UCLA Language Materials Project Language Profiles