The λ-calculus created in the 30s by Alonzo Church, ten years before the era of computers, is a small formal language theoretically allowing to build any algorithm one can think of. As any other language its implementation on a computer supposes an underlying language which itself is built on a lower one until the bare metal of the computer. Web browsers come with a rich set of tools, (HTML, CSS, DOM, JAVASCRIPT,...) on which I have built a small overlay, the lambdaway project, proposing an IDE, lambdatank, and a programming language, lambdatalk.
Using lambdatalk I progressively introduce in a wiki page a small working version of λ-calculus, starting from its simplest definition.