The meanings of Hebrew words (and several other Semitic languages’ words) are based on the root meanings of consonant sets, usually three to a root but that varies. Say ChRB is your root. ChaRiB might have one meaning, CheRuB another, ChoRaBai yet another, all related to a base meaning of “burn” (before being baby angels, cherubim were angelic figures characterized by flame). To give an English parallel, consider the related meanings of sheen, shine(n), shine (v), shone, shining, etc. All related in meaning yet all somewhat different words.
The alphabet derived from apparent cuneiform pictographs, where “beth” was a house, “aleph” a head of cattle, etc. As it moved to alphabetic use, it was a form of shorthand, each letter representing a consonant sound associated with the pictograph it was derived from. (That includes our own; ours derived ultimately from the related Phoenician alphabet, through a complex series of modifications.) Think of a child’s alphabet book: A is for apple, B is for ball, etc. Now imagine that the letters are actually stylized apples, balls, and so on.
As to how effective it was as a shorthand, it shd b vdnt tht U cn qckly rd A cnsnntl scrpt. (Notice the special characters, represented by uppercase, for short words that were vowel-only. Hebrew had two of these.)