Tvashtri is the Vedic answer to a question most pantheons ask sooner or later: who made the things the gods use. His name is an agent noun from a root meaning to fashion, so it says maker in the plainest possible way, and what he makes is specific rather than cosmic. He shapes the wooden cup that holds soma. He carries a well-made axe. He fits the shapes of creatures in the womb and is asked for good offspring. He is the one who gives form, and the hymns use his name in contexts where a craftsman rather than a creator is wanted.
The distinction matters because Vedic religion has other candidates for the maker of the world and does not confuse them with him. Tvashtri is a workman among gods, praised for skill, and skill in this material is a serious religious category: the Ribhus, three human craftsmen, earn divinity by taking his single soma cup and making four of it, which is an act of one-upmanship that the hymns treat as heroic rather than impious. Tvashtri's reported irritation at it is one of the very few moments of personality he is given.
In later literature he merges substantially with Vishvakarman, the all-maker of the classical tradition, and his name becomes one of the standard words for a divine architect. The Puranic lists of twelve Adityas keep him under his own name, which is one reason the older figure did not disappear entirely into the later one.