A politically emotive subject, I will attempt to present only facts here:

A Finland Swede is typically a person who is born and living in Finland, but whose mother tongue is Swedish. There are approximately 300,000 such people (about 6% of the Finnish population), but the number is slowly falling.

They are found chiefly in the South-West of Finland and especially on the Åland islands, which are monolingually Swedish. There are also a not-insignificant number of Finland Swedes in America, around Minnesota.

For those with an interest in Linux, it should be noted that Linus Torvalds is a Finland Swede.