A hot wallet is any wallet connected to the internet, such as a mobile app or browser extension. It is convenient for daily transactions but more exposed to hacking attempts, malware, and phishing because it is always reachable online.
A cold wallet keeps your private keys completely offline, usually on a dedicated hardware device or even a piece of paper. Because it is never connected to the internet during normal storage, it is far more resistant to remote attacks. The tradeoff is convenience: sending coins from a cold wallet takes a few extra steps.
A common approach beginners use is to keep a small amount in a hot wallet for spending or trading, and move larger long-term holdings into a cold wallet. This way, even if the hot wallet is compromised, the bulk of your funds stays protected.