Can you guys please answer completely..i read an answer to the same question but they used putExtra method..i don't know where it is used
The question you have asked involves a larger implementation with code.
Use ExoPlayer to play videos in android. You can learn it from this CodeLab and also check this for more information.
From your question i understand there is a cardView and when you press it, a video show play in another activity. So for this you need to know how to use Intents in android. Intents help in passing data(such as a video url) from one activity to another.
Also check this project which uses ExoPlayer to play videos from internet with URL.