The Picts were the inhabitants of Caledonia, north of the River Forth. They were given this name by the Romans. In Latin the word is Picti which means painted folk or possibly tattooed folk. They spoke a language, Pictish, of which little is known.
Modern scholars believe that there were seven ancient Pictish Kingdoms and that their names were
- Cait -- situated in modern Caithness and Sutherland
- Ce -- situated in modern Marr and Buchan
- Circinn -- situated in modern Angus and the Mearns
- Fib -- situated in the modern Fife and Kinross (Fife is still known as the Kingdom of Fife)
- Fidach -- situated in modern Moray and Ross
- Fotla -- situated in modern Atholl and Gowrie
- Fortriu -- situated in modern Strathearn and Menteith
However there is good archaelogical evidence and some written evidence that Orkney was also a Pictish kingdom.
From the 6th century AD onwards they came under increasing pressure from the invasion of the Dalradian Scots in the west and the Vikings in the east, until in 834 AD they were finally conquered by the Scots under Kenneth Mac Alpin.
For more on the Picts see the website Coed Celyddon 
You can often tell where Pictish settlement has taken place in the past from place names. Those prefixed with "pit-" indicate the region was inhabited by Picts in the past (eg: Pitmedden, Pittoddrie, etc)