Hot storage is covered under Hot Wallet, which explains how online wallets work, their main types and how to use them safely. This page gives a short definition and explains how the two terms relate.
In crypto, hot storage means holding the private keys that control funds on a device or system connected to the internet, such as a phone app, a browser extension or an exchange's servers. Keys stored this way can sign transactions within seconds, which makes hot storage convenient for trading, payments and frequent transfers. The trade-off is exposure to hacking, malware and phishing, since an attacker who reaches the device may be able to steal the keys.
The opposite is cold storage, in which keys are kept offline, for example on a hardware wallet or paper backup. Exchanges usually keep only a small share of customer funds in hot storage to cover daily withdrawals and the rest in cold storage. "Hot storage" describes the practice or the place where keys are kept, while "hot wallet" names the software or account that uses it; in everyday speech the two are interchangeable. The term is also used in data management for storage that is quick to access but more expensive than archive storage.