Minutephysics is known for, you guessed it, short physics videos. Recently, they've started a new series on relativity that's going to go much more in-depth than previous ones, partially inspired by series's by 3Blue1Brown (another excellent educational channel).
So far from what I've watched this is an excellent series that really does a great job explaining generally confusing topics in a easy-to-understand, and intuitive way. I highly recommend that if you are interested in physics even a little bit, especially if you don't know much yet to watch it. If I were to pick any one introductory piece, I'd recommend this one.