Comments and utterances such as "howdy" "hey" "what's up?" "awesome weather uh?" don't do much to give knowledge or anything. They are just tools for everyday conversations. What is this type of language called? Just "informal" or something else?
These 'social lubricant' words are called
They are intended to not convey information but simply mark a social need. Or rather the information is not based on reference to objects and actions but instead to conveying the social situation.
Of course it all depends on the situation. "How are you?" can be phatic, when the intention is to get the response "Fine. And you?", or it can be informative, when the intention is a description of one's hospital visit.
Vernacular is another word for it.
Informal and colloquial would refer to the form of the language used, including the speaker's tone, non-standard words and pronunciations. Small talk refers to the content of the discussion. Speaking just for speaking, on the weather and the like.
I would term this casual conversation.
In an unsearchable and potentially ephemeral comment to the original posting, Professor Lawler kindly presented the following answer:
These are markers of social class and ingroup solidarity, identifying the speaker’s status, and allowing listeners to “tune” the speaker’s voice.
The first few exchanges in most conversations would be lost to untuned ears anyway, so these are usually taken up with meaningless formulas for social tuning, and thus no communication is lost.
I’ve marked this posting Community Wiki because it is John’s answer not my own, and so I deserve no reputation from it.