The content network is the ad distribution network for Bing Ads running in Windows apps. When you create your campaign, you can choose to display your ads on this network.
Using the content network gets your ads in front of the wider Windows audience, meaning more potential customers.
If an ad for an clothing company has the keyword "dress" and the keyword "shoes" and there is a content network app related to fashion, the ad could display even though a person viewing the app did not search for "dress" or "shoes." That's where the content match type keyword works for you.
Any keyword you add will have the content match type (how a keyword is matched to a customer’s search query or app’s content), along with any other match type you select.