No one who speaks English has any difficulty understanding the meaning of a sentence like ‘It’s warm in here’. We all recognize that it is a comment on the temperature in some place or other. But why it is being said, and what the speaker wishes to convey by saying it, depends entirely on two things: the context in which it is said and what the speaker wants people to understand. Suppose, for example, that the words are spoken by someone who is either lazy, ill or in some position of power. ‘It’s warm in here’ might then be either a request or an order for someone to open a window. If, however, two people come in out of the cold, ‘It’s warm in here’ might well be an expression of satisfaction or pleasure. In each case, the sentence is performing a different language function, e.g. requesting, suggesting, etc.

(HARMER, Jeremy. How to teach English. Adaptado)