
It’s Blu-Ray. The difference is in the capacity of the disk. Blu-ray is up to 50gbs of data letting a higher quality video and less compression of audio. Not to mention more special features and such like deleted scenes. DVD max capacity is 8.5gb. Most DVD is 480p, standard blu-ray is 1080p or full HD.
Most Blu-ray players have a built in up-scaler. They’ll take the non HD picture and add in the missing details. If you’re on a 4k tv, the tv also does this. So you end up with a pretty clear picture even if it’s an older video. If you watched a movie on a DVD, then watched the same movie in 4K Blu-Ray you’d notice a huge difference