Reverse angle means opposite angle. In cinema, although it is usually used in dialogue shots of two people, the point to be noted is that the reverse angle is independent of dialogue and distance.
For example, the character enters the room, we see him in the general plan behind his back. he picks up a note from the table and the camera turns to the opposite angle, showing his face.
For general use, let's take a scene where one character is sitting on the sofa and the other is standing by the window watching him.
There is always an invisible line between these two characters. First character appears, then the camera turns 180 degrees in the direction of this line and moves to the opposite side so second character appears. Both shots can be the image of the other through the eyes of one, or the image of both characters through the eyes of the audience.
For the first case, the shooting can be done from behind the shoulder, for the second case, the character can be placed in the frame alone. So much so that sometimes there are counter-angle shots where both options are used at the same time. Counter-angle shots are often used abundantly in American cinema. In European cinema, it is not preferred much.