Help understanding data validation

My basic questions are what exactly is data validation as it relates to crypto, and how does it provide tangible value? Is data just sourced by people in the ecosystem? How is it then legitimately confirmed by a validator? What other projects make their money entirely off of the collection and validation of certain data?

I understand that the data for different projects is separate with respect for what the project is trying to do, but I want to understand how it is actually sourced, validated, and why that matters for things like DeFi. As far as I am aware Flux is trying to make a DeFi database, but is that information not already available to compile and consume? I just don’t understand how value is added by someone alleging validation.