I found my written down wallet address, but it seems the app doesn't exist anymore. Any tips on how I can get my (very small bit) money out?

When people first get into Bitcoin, there are a lot of concepts that sound simple until you actually try to understand how they work.

Things like:

• private keys vs. seed phrases 
• hot wallets vs. cold wallets 
• Bitcoin mining 
• transaction fees 
• self-custody 
• the halving 
• market capitalization 
• why Bitcoin has a fixed supply

I'm curious: what was the Bitcoin concept that confused you the most when you were getting started?

And if you understand it now, what explanation finally made it click for you?

I think collecting simple explanations from people who have already gone through the learning process could be useful for other beginners here.