Does walking or running make u lose more weight???

Ok now i know lots about exercise but there is one thing i still dont understand and believe. I heard that walking will make u lose weight and running makes u tone up. ok now i dont get it when i get on treadmill and start running i lose more calories quicker than if i was walkin on it so how does that work? i have had this question for ages and answers jst make no sense. please help coz id rather be walkin hehe. i wanna lose about 3kgs and tone up too