The ending -ㅂ니다 is a polite and formal form of the copula verb,-(이)다(=to be), and usually used in official documents, news or when meeting someone for the first time. Technically we call it "하십시오 style".^^'
For example,
1) Noun(ending with the final consonant) + 이다
I am Korean
= 난 한국인+이다 = 전 한국인 + 입니다.
('인' in "한국인" has the final consonant, 'ㄴ')
2) Noun(ending without the final consonant) + 다
This is coffee
= 이것은 커피 + 다 = 이것은 커피 + 입니다
('피' in "커피" doesn't have the final consonant, it just ends with a vowel, 'l')
Here are some other speech styles.
I am Korean
= 난 한국인 + 이다
= 전 한국인 + 입니다(formal, polite)
= 전 한국인 + 이에요(informal, polite, commonly used in spoken)
= 전 한국인 + 이야(informal, not polite, between close friends)
This is coffee.
= 이것은 커피 + 다
= 이것은 커피 + 입니다
= 이것은 커피 + 예요, not 이에요 (because 피 doesn't have the final consonant)
= 이것은 커피 + 야, not 이야(because 피 doesn't have the final consonant)
\^o^/