Heimosodat is a Finnish word that means "kindred wars". Like how we have friends and family, Finland has some neighboring countries that they consider to be their "kindred" or relatives, because they have similar cultures and languages. These countries include Estonia, Karelia, and Ingria.
During the early 1900s, Finland was still trying to become its own independent country, and to do this they sometimes fought wars to try to take control of their neighboring "kindred" lands. This was called heimosodat.
Imagine if you and your cousins lived in different houses, but you all shared the same favorite toys and games. One day, your cousins said they were going to take all the toys and games back to their house and not share them with you anymore. You might feel upset and want to fight to keep your toys and games. This is kind of like what Finland was doing with their kindred wars.
However, heimosodat was not always a good thing. Sometimes it caused a lot of conflict and hurt feelings between the different countries. In the end, Finland was able to become its own independent country without taking control of all their "kindred" lands.