If you've ever seen the kepler light curves... they're anything but constant. From any star.
Non-eclipsing binary stars have the same light curve, if their angular separation is smaller than the resolution of the circle the algorithms and programs 'look' inside for that particular 'star'.
Eclipsing binaries have fun light curves...
And shutter effect...
Basically all it is is two (or maybe more) stars orbiting in the same plane so that we can see the stars alternatingly pass in front of the other. Depending on the difference in brightness the dips may be the same or they may alternate in depth, with the smaller one meaning the brighter star is passing in front of the dimmer one. Even though it is brighter, when a star is not eclipsed, Kepler (or anything using photometry) detects the light from both stars.