"Lambda" Behind Functional Programming

I have been writing code in Imperative programming languages for many years. Writing code in functional programming is a big shift and change in thinking. As I recently started with Elixir and when I was reading about Functional Programming, I keep reading mention of Lambda Calculus every time. That ignited my curiosity to brush up my computer science knowledge. As Functional programming languages implement Lambda Calculus(λ-calculus). If we understand how Lambda Calculus notation works from Computer Science perspective it will be easier to understand Functional programming. As nowadays most of the languages have implementation of lambda calculus may it