As the price of NFTs began to rise and popularize in the news, more and more NFT marketplaces started to pop up—but most of them aren't decentralized. The most popular marketplace for NFTs is OpenSea, but it is entirely centralized.
This means that users have to rely on a third party to hold their funds and assets hostage, which is not ideal. You can't withdraw your funds or assets from the site until they release them back to you—and even if they don't outright steal what you give them, they could still lose it through negligence.
A better & safe option is to use non-custodial decentralized marketplaces like XANALIA or Looks Rare. These marketplaces store your NFTs and funds on the blockchain rather than holding them themselves, so you always have access to them in an emergency. These marketplaces allow users to transact peer-to-peer without going through a third party.