Resources
You could certainly do a Google search to find resources for these topics. But, top ranked items aren't always necessarily the best. And sometimes there are gems hidden within material related to other subjects.
The items here are curated to include courses, tutorials, blogs, podcasts, etc. that I've spent some time with and I feel are of high quality.
Connect with me on Twitter to share your favourite resources.
APIs (Application Programming Interfaces)
YouTube: MuleSoft Videos
What is an API? Uses a waiter in a restaurant as a great analogy to explain what APIs are and how they work.
Binary Digits
Harvard University: CS50 (free course)
In Week 0 of CS50's Introduction to Computer Science professor David Malan uses lightbulbs to demonstrate binary numbers (starts at 07:43 in the video).
Pluralsight: What Is Programming? (free course)
In the Introduction check out: So What's the Deal with All the 1's and 0's?
base.cs Podcast
Bits, Binary, and Bytes from Season 1 of Vaidehi Joshi's podcast.
CSS Flexbox
Smashing Magazine
Rachel Andrew's (@rachelandrew) excellent series takes a close look at Flexbox's features and attributes:
Emacs
YouTube: DistroTube
The Basics of Emacs as a Text Editor Walkthrough of common Emacs commands. Video description includes a good, brief cheatsheet of the many commands covered.