boolean between faces?

I’m asking to learn if there is any way to do boolean between faces.
How i can do union, difference or intersect between 2 faces of the same mesh?

boolean between faces.
Show what this means rather than us having to guess which of the many possibilities you are actually wanting. Don’t be so terrified of supplying things like diagrams, screenshots etc etc etc

Booleans work between two separate objects

here is the image of the selected faces that i want to boolean.
i want to move these faces at -y and make them 1 with the faces that you can see at the bottom.