Reconfirming by phone same as checking in 3 hours prior?

I booked with cheapoair and going from chicago to houston then houston to san pedro sula, honduras so its international anyways back to my question it said this:"For International Flights, please reconfirm your flights 72 hours prior to departure. It is recommended to check in 3 hours prior to departure for all International Flights." Is it the same thing? can i do either one? or do i have to call? or just go check in?