If something is "relatable", it means that you have an understanding of the subject based off of similar experiences in your own life. If something is "relatable", it creates a certain level of empathy. Hope this helps :)

It is an adjective applied to someone or something you can "relate" or "connect" to in some way, but there is some level of discussion in English language circles how "proper" a word it is. Its use is growing over time, especially among younger people, but you may encounter an English teacher who says it's improper.