Break Lights do not work when lights are on

So I have the same problem right now on a 2001 Tacoma, I’m sorry if I’m not understanding or I’m stupid. But what does this mean “Now I have brake lights no running lights, test fuses, replace, back to no brake lights. Pull tail lights, pull wires for brake and running lights, swap positions in switch. Now everything works. So when putting in after market please have someone check all functions.” I know he’s trying to explain but I have no idea what he’s saying lol please someone help cause it looks like he figured it out. Thanks