Daedalus is a full node wallet. This means that unlike light wallets (e.g.Yoroi, Adalite etc.) Daedalus downloads a full copy of the Cardano blockchain and independently validates every transaction in its history. That way you get maximum security and completely trustless operation, without centrally hosted 3rd party servers.
Yoroi is a light wallet for Cardano. It’s simple, fast and secure. Yoroi is an Emurgo product, engineered by IOHK. And it follows best practices for software in the industry including a comprehensive security audit. Daedalus and Yoroi are complements to what they try to achieve. Yoroi looks to be a day to day wallet for a Cardano user.