what is modern data stack for freshers?

this one is gold - https://www.getdbt.com/blog/future-of-the-modern-data-stack/

You should check out https://www.thoughtspot.com/blog/what-defines-the-modern-data-stack-and-why-you-should-care

Here's landscape summary that we've been keeping up to date at Portable: https://portable.io/learn/modern-data-stack