質問: When are ます and です used? Are they interchangeable?
回答: ます is used when someone or something DOES something, for example: the dog walks 犬は歩きます. です is used when something IS something, for example: the bed is blue ベットは青いです. Also, just as extra information, です and ますare used in the present and future tense. This ending makes the sentence you are saying more polite and formal.