read in the book: i.e. the Hebrew text of the Pentateuch. See App-47.
distinctly. a distinct [reading], i.e. (according to the Talmud) translating and interpreting it in the Chaldee paraphrase.
and. Note the Figure of speech Polysyndeton (App-6), to emphasize each clause.
gave the sense: i.e. divided the sentences, &c, according to sense.
caused them to understand the reading: i.e. gave the traditional pronunciation of the words (which were then without the vowel points).