Balancer is a DEX exchange that uses automated market making to perform swaps like Uniswap. The big difference is in how it handles liquidity pools.
With DEXs like Balancer and Uniswap users put up tokens as liquidity and then this is used for the trades of other users. This is automated market making.
WIth Uniswap you have to put up tokens in a 1:1 ratio (so $500 of ETH and $100 of DAI for an ETH/DAI pair for example), with Balancer you can put up your entire portfolio and offer unevenly weighted liquidity.
In short, Balancer (and this is where the name comes from) differentiates itself by being able to handle unevenly weighted liquidity. Because of this slippage can be higher, but also different opportunities present themselves and it is more friendly for the common user who doesn’t necessarily want to hold an equally weighted portfolio. Speaking of which, if you are a long-term holder, you can simply put up most if not all of your ETH-based assets in Balance and earn liquidity fees. There are risks, but this is yet another draw of Balancer.
Long story short, you can use Balancer for simple swaps, but its main use-case is the above.
"Balancer" contains information about the following Cryptocurrencies: