Do you know what the word "advantage" means?
Think about whether you understand the meaning of this word.
If you have thought about it and succeeded, that is a very good result.
Congratulations, you can now start playing.
The house edge is the term that defines the advantage that a casino has over the player in any long-term game. That's why they say that the house never loses, that's why I think that casino games should be seen as fun, and playing only with money they don't need, is like going to the amusement park, you spend money but you don't care.
They have an advantage because they dont want people to be long-term profitable because that could lead to financial losses for a casino. So they created a house edge to solve this problem.