감사합니다（kam sa ham ni da）is usually used when you say "thanks"to somebody who you want to respect and you meet the people at the first time. 고맙습니다（go mab sub ni da）is usually used betwen your friends who you are know them well and it expresses your friendship.you also can say "고마워요"(go ma wo yo) to express your thanks~~

고맙습니다 is less formal than 감사합니다, but it's still formal as compared to 고마워요(-요 is a respectful ending). -ㅂ니다 isn't virtually used between friends. You can say 고마워 to your very close friends.

same ------ "thank you" = "감사합니다." = "고맙습니다."