The prefix "ter-" can mean that what happens occurs by accident or involuntarily. But since falling is usually by accident, there's no difference in meaning between jatuh and terjatuh.
Please note that when combined with other words, we usually use "jatuh".
I fall in love = Saya jatuh cinta (not terjatuh cinta).
I fall backwards = Saya jatuh terjengkang (not terjatuh terjengkang).