At one time I could save You TUbe videos but they stopped that for the most part.
THere are still SOME you can download for later playback but Streaming means **************. bad connection. over limit on your data plan. Sorry but BUFFERING will be the most common display. Good connection not over limit it work great.
But Streaming is kind of like LIVE TV. v/s recorded.
That said there IS a way (usually) to save it. but .. If you have to ask It's beyond me to explain it..
I do more Audio than video and I am able to save most anything. Sometimes with "Generation Loss" sometimes bit perfect. Depending on how much Effort I put into it and how much I spend on softare and hardware.. I used to produce recordings of/for my daughter and thus had to be able to break copy guard since the best recorder I had copy guarded everything.