Emotions can be a hard topic for kiddos to understand. There is nothing concrete to which you can point and label it “happy.” This doesn’t make talking about emotions any less important. As kiddos grow and develop they learn new words, they gain new skills, and they feel different emotions. Labeling these emotions can help them understand what they are feeling, and why. And just like learning anything else, it may take practice to understand. So talking about emotions needs to happen regularly and needs to start when people are calm. Understanding something new when we are already upset is hard for anyone but especially hard for our little ones. It may be helpful to try to use a Feelings Wheel with pictures to make this concept of emotions more real.
For further reading on this topic check out this article from Understood.org