Free morphemes:
lexical: nouns, verbs, adjectives, (most) adverbs
functional: pronouns, prepostions, articles, conjunctions, auxiliary verbs, etc
Bound morphemes:
derivational:
changes meaning and/or word class, e.g. dis-, un-, im-, -less, ness, etc
inflectional: has a grammatical function: -s, -ing, er, 's, etc