Self-custody
Also: non-custodial
Self-custody means you control the private keys to your funds yourself instead of trusting an exchange with them. Such wallets are called non-custodial. Examples include apps and browser extensions such as Phantom, Solflare or MetaMask, and hardware wallets that keep keys on a separate device.
Trading memecoins on a DEX requires self-custody, because you sign the swap from your own wallet. The upside is full control: nobody can freeze your account or go bankrupt with your funds. The price is full responsibility. There is no helpline to reverse a mistaken transaction or recover a phrase. So it pays to split funds: a working wallet for trading with a small balance, and a separate one, ideally hardware, for savings.