Hot wallets are wallets that can be connected to the Internet, while cold wallets are kept offline at all times. Funds stored in a hot wallet are more accessible in comparison to funds in a cold wallet but it will have lower security.
Hot wallets are wallet you generally see as an App or on your PC. As your phone or PC are connected to the internet at all times, it is easy to send or receive funds. However, online devices can be hacked easily.
Cold wallets are devices that are made especially to generate and hold your private keys. They are always offline so hackers cannot access your information.