IPA: /ˌɪn.fəˈmɜːr.ʃəl/
KK: /ˌɪnfoʊˈmɜrʃəl/
A type of television advertisement that is longer than a typical commercial and often includes demonstrations or discussions about a product.
The late-night infomercial convinced me to buy the new kitchen gadget.
Infomercial is formed from "info-" (short for information, derived from Latin "informare", meaning to inform) and "commercial" (from Latin "commercialis", meaning pertaining to trade). The word refers to a television program that provides information about a product while also promoting it for sale, blending information with commercial intent.
Think of 'information' ('info-') being presented in a 'commercial' format — that's how an infomercial combines both elements.