What are these words known as? – the, of, and, a, to, that, it, with, but, they, she, he

The words listed (the, of, and, a, to, that, it, with, but, they, she, he) are high-frequency words that learners need to recognise instantly without decoding. These are called sight words because they should be recognised 'on sight.' The Dolch and Fry lists include such common words. They are not unimportant — they are essential building blocks of English. 'Form words' and 'use words' are not standard linguistic terms.