As someone who studies this stuff, I can't resist - reading this thread hurt my brain too badly.
Both Ritalin and Concerta are trade names for methylphenidate. Methylphenidate is the name of the compound (the generic name), and different companies make pills that have methylphenidate as the active ingredient. Ritalin/concerta both are 'the same drug' and 'have the same mechanism' - delivering molecules of methylphenidate to brain.
The only difference is how slowly methylphenidate is released/absorbed into the blood. Think of it like the difference between chugging a beer on a full stomach vs empty.
Adderall is a different drug altogether - amphetamine salts - that works through a similar, but not the same, mechanism.