OpenSea is a marketplace for digital goods or NFTs, including collectibles, gaming items, digital art, and other digital assets that are backed by a blockchain like Ethereum. On OpenSea, you can buy, sell, and trade any of these items with anyone in the world. OpenSea is currently the largest general marketplace for user-owned digital goods, with the broadest set of categories (200 and growing), the most items (over 4 million), and the best prices for new categories of items. OpenSea is also a decentralized marketplace. Trading on OpenSea happens through a smart contract, meaning that no central authority ever holds custody of your items.

There are multiple ways to earn returns on OpenSea. The website is an open marketplace, so like the stock market, you can buy digital assets in hopes of appreciation. Another way to earn money is by creating digital assets yourself and being the original seller of the item. You can also help broker deals by finding a buyer for a seller. If you match a buyer and seller, you will receive a small percentage in royalties for your help.

The platform charges a 2.5% fee on all transactions. OpenSea's most commonly used currency is Ethereum so it's likely they have Ethereum holdings that have increased greatly in value over the past few years. Also note that due to Ethereum's popularity, gas fees are high so transactions are expensive to execute.

OpenSea has a strong track record as a safe marketplace for unique blockchain-based assets. They have had over 40,000 ETH of volume pass through their smart contract and many thousands of successful sales. They have acted as the primary marketplace for several large games, including Etheremon Adventure, My Crypto Heroes, CryptoVoxels, ChainBreakers, Ether Kingdoms, and CryptoBeasties -- as well as a secondary market for CryptoKitties, MLB Crypto, Axie, and a host of others. For the more technically savvy: They leverage the Wyvern Protocol, an audited, battle-tested set of smart contracts. Wyvern is a decentralized exchange system that creates a personal proxy for each user. They don't control the proxies that get created, and you have to approve access to each ERC721 contract individually. Once the contract is approved, the logic of the exchange contract only allows it to transfer an asset from your proxy if both apply:

1. You have signed an order indicating you wish to sell that item.
2. It is properly matched by a buyer paying the appropriate funds. So not only does your asset not leave your wallet until it is sold, it is only allowed to be swapped if an order you create is properly matched.