That was layman's terms..!
Difficult to put more simply, but the Power Supply Unit (PSU, or 'brick'...) is rated to be able to supply up to a certain current (expressed in amps ('A'...), or milliAmps ('mA'...). Any pedals connected must draw (consume...) less, when added together, than the PSU can deliver. So, as an example, a PSU rated for 500mA is OK for one pedal drawing 100mA, or even up to five at a push (but no more; best to have a small margin, so four would be a better limit...), The same PSU can supply a single pedal consuming 300mA, but not two of 'em. Is that clear enough now..?