Q. How to use the Track Mattes feature in After Effects to leverage still images & video clips?

SOM did a good writeup on this:
https://www.schoolofmotion.com/blog/how-to-use-track-mattes-after-effects

Also, this is a pretty basic skill to have in AE. I'd recommend taking an AE course so you have all these core concepts under your belt, here are a few options:
https://www.schoolofmotion.com/after-effects-kickstart

http://www.videocopilot.net/

https://www.pluralsight.com/courses/after-effects-cc-2017-fundamentals

Hi there,

I am a Senior Designer at techjockey.com and consider it my duty to guide you through this. So here you go,

To use the Track Matte, you'll need two layers:

The top layer will provide the alpha, or luminance, information

The bottom layer below will act as a fill

Only the bottom layer content will be visible and the top layer will be used to create Borders.

You will get these Track Matt options in After Effects, which you can use whenever you want to use a text layer into an image as a controlled 'window'.

• Alpha Matte which helps use the alpha channel of the above layer as a mask for the lower layer.
• Alpha Inverted Matte allows using the negative space around the alpha channel in the above layer.
• Luma Matte that makes it possible to use brightness and luminance as a mask for the bottom layer.
• Luma Inverted Matte to do the opposite.