Base is an Ethereum Layer 2 network built by Coinbase.
Base will serve as both a home for Coinbase’s onchain products and an open ecosystem where anyone can build.
Base uses ETH as payment for network fees. You can explore transactions done on the Base network using https://basescan.org/
The Uniswap web app now supports the Base Network. This means anyone can swap and provide liquidity using the Uniswap Protocol on the Base Network.
Learn more about this in these Uniswap Help Center articles: