Uniswap v2 is a decentralized exchange founded in 2018 as an iteration of v1. Uniswap is based in the US and support multiple crypto assets including both major one like Bitcoin and XRP but also very many altcoins numbering into dozens.
It is an onchain liquidity protocol on the ethereum block chain on which easy and convenient token swap can be done without any need for third part intervention. Being a protocol on the ethereum block chain makes it a source of boom for defi and dapps which are very many on the ethereum block chain little wonder then why people that use uniswap v2 are mostly user of one defi or dapp. It provides easy swap of token for them.
One great advantage is that token swap does not cost asbmush as it would on other exchange. Uniswap v2 only charge network fee and no withdrawal fee.