Icon Issue

[Summayah5FC7]

I have downloaded this icon from adobe stock. But don't understand how they made it.

The outline is made by placing one shape over the other.

Both are grey, but when the smaller grey shape is placed on top of the larger grey shape. The colour changes to white.

I've looked at the opacity settings and it is normal.

[Ton Frederiks · Accepted solution]

This is a Compound path or shape, The interior does not change to white, but becomes translucent.

https://helpx.adobe.com/illustrator/using/combining-objects.html