Bitcoin mining difficulty

Hi BTC community,

I'm making a free tutorial on how BTC is working for beginners...

Thus, I would like to cover many subjects, among which the "Mining Difficulty".

I understood that the Difficulty = Current Target / Max Target

Questions

• Where can I find the Current Target? How is the current target defined?
• Why is the MAX target fixed at 00000000FFFF00000000000000000000000000000000000000000000000000000 and not F's only? which would be the highest hexadecimal figure
• How to interpret the Difficulty figure?
  • For instance, today we have a difficulty of 36,950,494,067,222.
  • What does this figure mean exactly?
    • Does it mean that we would need an average of 36.950 TH as hash power to find the target hash?
    • I can see that an average ASIC has a hash power of 166TH/s, thus, it would take 0.21s to find it out... which is not logical... where am I wrong? :-D
  • (Current difficulty source: https://api.blockchain.info/charts/preview/difficulty.png?timespan=1year&h=405&w=720)

Where can I find resources detailing these concepts? I could not find resources explaining such details...

thanks in advance for your help