Uncertainty and cat

Heisenberg's principle states that

  We can't know both the position and momentum (speed) of particle with certainty.

Now did you understand that? I didn't and youtubed. The first video I watched explained a lot about dual property of objects of behaving like waves and particles. How if we observe the position, a single photon will modify the momentum. So the uncertainty of position multiplied by uncertainty of momentum is a constant. If we know one for certain, the other one will be uncertain - etc. 

I liked the first comment on that video though - Heisenberg called it uncertainty principle because no one can understand this principle. 

And then there is Schrodinger's cat which is said to be in a box both dead and alive. Nope, can't explain it either.