A hot wallet is connected to the internet — a phone or browser wallet, or your exchange account. It's convenient for small amounts and spending, but being online means more exposure to hacks and scams.
A cold wallet stays offline — typically a hardware device. It's the safest place for larger, long-term holdings because your keys never touch the internet. The trade-off is a little less convenience and a small upfront cost.
A common beginner setup: keep a small, spendable amount in a hot wallet, and move larger savings to a cold wallet once you have a meaningful balance. Whatever you choose, back up your seed phrase offline and never share it.