What is the function of language?

Language is a system of communication, so its main function -- its use or purpose -- is semantic: Language is a way to encode a particular meaning in symbols (like words) and transmit this meaning to others.
But people who study language want to take a much deeper look. What different kinds of communicative functions does language serve? And do people use language for other reasons, reasons that have little to do with communicating a specific meanings? Different scholars come up with slightly different lists, but they can agree on these basic points.
1. Language has many functions that derive from the semantic, or meaning-encoding, properties of language . People use language to
communicate facts, opinions, and propositions, including statements about abstract concepts.
       The tree is green. Nature is beautiful.
make requests and ask for specific information;
       Could you please hand me the binoculars? Is that a squirrel in the tree?
issue commands;
       Get down out of the tree!
convey emotions and intentions;
       Your arrogance makes my blood boil.
elicit feelings from others (by writing evocative poetry or prose);
       In the morning glad I see / My foe outstretched beneath the tree.
communicate about things that aren't immediately present (because they are located somewhere else, belong to the past or future, or are products of the imagination).
       I wonder if there are any trees on Mars.
Nonhuman animals have systems of communication that can perform some of these functions. For instance, vervet monkeys have alarm call vocalizations that reference specific predators (one means something like, "I see a snake!"). Bees can tell their companions the location of a distant food source by performing a ritualized "waggle dance." But in general, human language stands out for several things, like its ability to address abstract concepts, the past, the future, and hypothetical situations. These functions may be unique to language.
2. Language also serves several non-semantic functions.
One example is "phatic" language, the "small talk" we use in order to establish a mood or be polite. When people meet and say "How do you do?" they aren't really asking for information. The words are essentially empty placeholders. The speech functions as a polite gesture of greeting.
Another  example is the language we use in formal rituals, as when a Catholic priest officiates at a baptism. Although the words may have meaning relevant to the ritual, the priest isn't speaking them primarily to inform people at the ceremony.

The function of language is communication. In its written, verbal, and bodily performative forms, language communicates information based upon a shared set of symbols. Bodily language is not exclusive to humans, and many non-hominid animals rely on physical gestures and posturing to convey meaning. In humans, bodily language may communicate feeling, greetings, fear, or even complex thoughts, as in Sign Language. Verbal language is the most common form of communication used by humans, but it has the disadvantage of being temporally and spatially bound. Technology can help overcome this boundary by recording verbal information to be played at a later date. Writing has the benefit of being static throughout time and space, but it requires one to be literate to understand the written information.
Language is not limited to communicating factual information—it is also used to express emotion, establish and reaffirm identity, and for imagination.
https://www.britannica.com/topic/language