As much as I've learned about bitcoin the fees is what still threw me off. Awaiting an unconfirmed transaction to my ledger wallet and getting nervous. I see the value in holding various currencies. hmm.
Try watching some simple video about how does blockchain work what are blocks etc. In short transactions are gathered into blocks, blocks come every 10minutes, blocks are full now because they have a limit of 1mb per size (more transaction means transaction size is higher). So in order for your transaction to be confirmed faster (you get confirmation when your transaction enters a block) you need to put higher fee as with higher fee higher the chance is that your transaction is included in a block. Behind this is the really powerful crystallographic functions that enables all of this to be done and to be secure.