jam / jamb 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. 👇
jam: (noun) preserve of crushed fruit. (verb) push down forcibly. (verb) crush or bruise. (verb) interfere with or prevent the reception of signals. (verb) get stuck and immobilized. (verb) crowd or pack to capacity.
jamb: (noun) upright consisting of a vertical side member of a door or window frame.
jam: jh·AE·m
jamb: jh·AE·m
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)