fleas / flees are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
fleas: (noun) any wingless bloodsucking parasitic insect noted for ability to leap.
flees: (verb) run away quickly.
fleas: f·l·IY·z
flees: f·l·IY·z
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)