I found some sort of answer to the question here, but did not understand the procedure at all. May be some on can help me understand it.
I have one mesh with a face of it selected and I want to "glue" that face to a selected face on a different mesh. For example, suppose two cubes are facing each other and I want to glue the faces that are facing each other to one another, or suppose I am modeling a starship. The wings are one mesh, and the body is another mesh. Now I want to connect the body and the wings permanently at a very specific place on each. I thought to choose the faces on the wing mesh and on the body mesh that should be glued together and then blender glues them.
Something like this.