Confused about ETH2 staking rewards.

I just got off the waitlist and am now able to stake ETH2. I’m excited to start but I don’t understand what it means when I won’t have access to trade/sell my ETH. Does that mean that once I start, all the money I have invested in ETH is stuck on Coinbase until further notice? Or is it just the staking rewards I get for holding ETH that I won’t have access to? For me, the rewards will most likely be pennies, so I don’t care if it’s held. It’s just all the money I’ve invested that I’m worried about not having access to. Thanks for your help!