Lambda (λ) calculus primer: from the basics to complete programs

https://www.youtube.com/watch?v=9MtE5ONrQyk

This is the landing page for the "Lambda Calculus Primer" series of articles.

Articles (links will be updated as articles are published):

1. What is the lambda (λ) calculus (conceptually)?
2. Defining a function as a lambda (λ) abstraction.
3. The simple untyped lamda (λ) calculus (definition).