Things I Don't Understand

An incomplete list... I could probably look quite a lot of these up
  1. The running man challenge
    Why r they doing this what does it mean
  2. People who enjoy exercising
    Teach me your ways
  3. Most of maths
  4. Tinder
  5. This
    ?????
  6. Space
  7. How was fabric invented
  8. Electricity
  9. Why I'm not Louis Theroux
    Seriously, why???
  10. How planes don't fall out of the sky
  11. How the internet works
  12. Why is my cat always tired when all she does is sleep??