What is" co-operative advertising" in marketing?

AGREED WITH MR. ALEX YAZOURI

Cooperative advertising is a cost-effective way for manufacturers, retailers or distributors to reach their target markets.

Advertisements by retailers that include the specific mention of manufacturers, who in turn repay the retailers for all or part of the cost of the advertisement

I agree with mr. Alex that its one of the cost effective way for manufactures and distributors to reach their target audience 

It is not very clear what yo are asking for. I believe your questions should be more elaborate, rather than just asking for definition you could just Google. Try to relate your question to a specific project or issue.

Co-operative advertising, is when a manufacturer agrees to repay a retailer/ distributor all or part of the advertisement costs that the retailer  used to promote the manufacturer's products.

AGREED WITH MR padmakumar pathiyil

Co-operative advertising, is part of marketing about product sell and services.

A product's manufacturer and a retailer share the costs of Ad compaign on a specific product. 

Cooperative advertising is a cost-effective way for manufacturers, retailers or distributors to reach their target markets. Although co-op advertising policies differ from manufacturer to manufacturer, most will pay a portion of the advertising costs and supply the retailer with photos or graphics to use in the ad (or sometimes the entire ad itself), whether for print, radio or television. A manufacturer's contribution to a cooperative advertising campaign can range from a large amount of money to promotional gimmicks and point-of-purchase displays.

Using co-op advertising cuts down not only on your media costs but also on your ad production and creative expenses as well. A smart advertiser will factor co-op advertising, if available, into his or her budget. The major drawback to co-op advertising is that some manufacturers have more restrictive programs than others.

Another form of cooperative advertising is sponsored by shopping districts or centers, which feature an advertisement from each retailer in the shopping center. These promotions are often found in local newspapers for back-to-school specials, St. Valentine's Day, Fourth of July, Mother's Day, Father's Day and so on.