The BNB Chain is a Layer 1 blockchain that allows anyone to deploy smart contracts and build dapps (decentralized applications) on top of.
Other names for this chain include the BNB Smart Chain and the BSC Chain.
Anyone can use a crypto wallet to swap, provide liquidity, or hold BEP-20 tokens on the BNB Network using different dapps.
The Uniswap web app now supports the BNB chain, which means you can swap and add liquidity using the BNB Chain.
Learn more about this in these Uniswap Help Center articles: