What it is
Advertising inside a retailer’s own environment — sponsored placements on Amazon, Walmart, Instacart, Target and dozens of others — sold using the retailer’s purchase data. It is the closest thing in advertising to buying shelf position, with better measurement.
The growth is real, and so is the reason for it: the data is first-party and the conversion happens in the same place as the ad.
The one question
Do you sell a physical product through that retailer? If yes, retail media is not optional — it is table stakes, because your competitors are bidding on your category page and organic placement alone will not hold position.
If no — you are a service business, a restaurant, a practice, a contractor — retail media is not your fight. There is no shelf to defend.
If it is yours, three things matter
Defend your own brand terms first. Competitors bid on them, and losing your own name is the most expensive placement to lose.
Then category terms, where the volume is and the cost is higher. Expect to pay for share.
Then your product detail pages, which convert the traffic you just bought. Retail media pushed to a weak page is a donation.
If it is not yours
Ignore it, and be slightly suspicious of anyone pitching it to a local service business. The equivalent moves for you are the boring ones: local search, reviews, a complete profile, and being present when someone in your county needs what you do.