Classical conditioning is where you learn to associate stimuli. This is something that happens to me all the time but one specific example is that I used to listen to a specific playlist every time I played a certain videogame. After about a week or so every time I played that game I would think of those songs and any time I heard any of those songs I would think of that game. There are still times now that I will hear a song and it will trigger memories of things I used to do when I heard it. This is a perfect example of classical conditioning. My brain associated the two stimuli and now whenever I encounter one I think of the other.