Latvia is rather neatly divided into two large groups: indigenous Latvians who make 62,1% percent of population and Russian native speakers who make up 37,2%.
The two communities are greatly divided. They have separate political parties, cultural activities, schools, opinions about history and much else. Latvians cherish their “miraculous independence” and indigenous culture, looking westwards politically, while many Russophones long for Soviet Union where they had a privileged role.
The remainder of Russophones are Latvia‘s other minorities which were unable to withstand the Soviet russification policies, gradually joining the Russophone „nation“. Only 0,7% of Latvia‘s population speak some other language than Latvian or Russian at home, even though 11% of its population are neither Latvians nor Russians.
The largest among these smaller ethnic primarily Russophone minorities are Belarusians (3,3%) and Ukrainians (2,3%), both descending from Soviet settlers. Poles (2,2%) arrived in pre-modern era of Polish-Lithuanian influence over Latvia. Some Lithuanians (1,2%) are indigenous while others were attracted by Latvia being the center of Baltic States (especially true in the 19th century).
All-in-all, a diagram of Latvia‘s ethnic composition over the past few centuries looks like some sad roller coaster ride (knowing that the most radical declines and inclines were made by expulsions, murders and colonial settlement rather than voluntary decisions).