An "explainer" is someone or something that helps make something complicated or confusing easier to understand by explaining it in a simple and clear way. Full definition
Watch this short explainer video on the price movement of Bitcoin — Question is, what will the Bitcoin price be in November 2017 and 2018? (bit-media.org)
Watch our video explainer on how the ECB is helping the financial system stay safe by encouraging «ethical hacking»... (ecb.europa.eu)
(You can watch a video explainer of the experiment here.) (sciencenews.org)