gel / jell 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. 👇
gel: (noun) a colloid in a more solid form than a sol. (verb) become a gel.
jell: (verb) become gelatinous.
gel: jh·EH·l
jell: jh·EH·l
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)