Rhythm and meter are 2 kinds of literary devices in poetry.
The word rhythm has its origins in the Greek word rhythmos, meaning “measured motion". As a literary device, rhythm displays short and long patterns by making use of stressed and unstressed syllables. It is organized in verses.
On the other hand, meter is a syllabic pattern which can either stressed or unstressed in a verse, or inside a poem's line. Stressed syllables often have a lengthy duration, whereas unstressed syllables have a short duration. In verses, meter functions as a pattern of sound for words, giving a pleasing and rhythmical tone to poetry.