Balancer is a non-custodial portfolio manager, liquidity provider, and price sensor.
Balancer turns the concept of an index fund on its head: instead of paying fees to portfolio managers to rebalance your portfolio, you collect fees from traders, who rebalance your portfolio by following arbitrage opportunities.
-- Whitepaper --
(This image was created using CalcPlot3D, a tool by Paul Seeburger)