Am I missing something ?!?
Yes , all the threads in which this has been explained 100 times over.
It's about scaling. Bitcoin needs to "upgrade" as it has reached it's current limit.
It has been known for years that we will hit this point.
How is actually using bitcoins even possible with a $3 fee.
When you transfer 10000$ it's not that much of a fee isn't it?
Are there some kinds of bitcoins transfers that are lower fee and other higher fee ?
Yes, one with high fees that get confirmed in 10 minutes and ones with low fees that take 3 days
I saw the words "on-chain" and "off-chain", maybe those words are key to different rates of bitcoin transfer fees?
No, nothing to do with fees.
Off chain transactions are not included in the blockchian so they basically aren't carrying a fee at all.