The Scottish National Party, shortened to SNP, are a centre-left political party who are strongly in favour of greater independence for Scotland. Founded in 1934, the first member to be elected to the British parliament at Westminster was Winnie Ewing who won the Hamilton constituency seat. They currently have 35 elected members in the Scottish Parliament, making them the opposition to the controlling Labour and Liberal Democrat coalition.
The SNP website
Other political parties in Scotland, and their nature: