Reading Shakespeare has great personal value, but for most people it has little practical value. Unless you are an actor or professor you can't actually do anything with your knowledge of Shakespeare.

"Theory" is associated with thought. "Practice" is associated with really doing something, with real things in the real world. A doctor may have a degree in medicine, but he is only "practicing medicine" if he sees and treats patients. In theory, you could improve the fuel efficiency of a car by filling the trunk with helium balloons, making it a few grams lighter. But that is not "practical." Something is of "practical value" if you can apply it and use it in real life. It is personally rewarding to study medieval literature, but it is not of much practical value. Knowing how to fix a leaking faucet is of practical value, because faucets often leak, and you often get an opportunity to use this knowledge.