So, I have run into this situation, and I believe many of you guys would have as well, that if I go to say Coinbase and go to my BTC wallet and click Receive, I get a BTC address where people can send BTC to my address. I have noticed that after a day or so, when I go back to my Coinbase again and click Receive, this address changes.

My question is, after the address has changed, if someone sends me BTC to my old address, will I still get it? Why does this address change dynamically? Is there a way to keep this constant?