If you have used Adobe Photoshop you have probably seen that it allows users to draw (or create content) in different layers. These layers can after be combined in many different ways, the blend modes. https://en.wikipedia.org/wiki/Blend_modes.
The blog post you are reading right now builds on top of the idea of having a branchless RGB to HSL conversion (http://www.poljeremias.com/branchless-rgb-to-hsl), and it proposes branchless solutions to the most common color blending operations.
If you want to just play around with it, visit the following Shadertoy, there you can try live the different branchless blending operations : https://www.shadertoy.com/view/Md3GzX
This post contains implementations for the following blending operations :