In the late 70's, we had the Betamax; then came the VHS, which was later replaced by the CD, and then the DVD. Now, we have the blu-ray.
Blu-ray discs which superseded the DVDs, have more storage space compared to the DVDs which regularly have only 4.7 GB of space. Blu-ray discs can store up to 27 GB which also means that it has more features and sharper details than the regular DVD.
To be able to enjoy these features, one must watch them in bluray players, which can also be used to play DVDs.