The terms are used interchangeably by most agencies and both platforms today, but there is a technical origin to the distinction. Retargeting traditionally referred to pixel-based tracking — someone visits your website, a pixel fires, and they are later shown your ads across other platforms. Remarketing, in Google's original use, referred to re-engaging people from your existing customer or email lists through Customer Match. Today, both Google and Meta use these terms to describe the same broad concept — any campaign targeting users based on a prior interaction with your business, whether that interaction happened on your website, your YouTube channel, your Instagram profile, or your customer database. In practice, when you hear either term from an agency, they mean the same thing: campaigns targeting warm audiences who already know you.