How do I use Alpha Channels?

General Color Context
Every color (pixel) within an image has 3 channels; Red, Green, and Blue. When dealing with 16 million colors (you will deal with 16 million colors usually), these values range from 0 (none of that color) to 255 (the max of that color). The RGB channels for red are (255,0,0). White is (255,255,255). Black is (0,0,0). You can create lots of different color by specifying different levels of Red, Green, and Blue.

Alpha Channels
Alongside the RGB channels is a channel which allows for semi-transparency of individual pixels (the alpha channel). Similar to the RGB channel, the Alpha channel value ranges from 0 (invisible) to 255 (fully visible). In MMFusion, alpha channels are represented as a grayscale with black being increasingly invisible and white being increasing visible. The resulting RGBA channel allows you to specify virtually any color at any level of visibility within an image.

When to use them
As far as I am aware, there isn't a need to use them but there can be places where using them is beneficial. In the Picture Editor, you can manually either the RGB values of an image or the alpha channel of an image. You can edit the alpha channel of an image by clicking "Semi-transparency" symbol on the left-hand column of the Picture Editor. During runtime, some extensions may allow you to modify the RGBA channels of an image.

To add:

I've used them around things like a firey torch and it can look really cool. Once you draw your alpha shades (like around an object or whatever) you can then pick a color and use the "fill" paintbucket in the editor to turn your default black / grey shades to shades of that color. So in my example, shades of red around the torch's fire.

One word of warning though is if you have an old-ass computer like me too many objects with alpha channels will slow everything down a ton.

Thanks for info. Me too needed to understand about alpha channel.