Google can show your search campaigns across two different areas.
1) Google Search: These are Google Search owned properties such as Google.com, Google.co.uk, and so forth for various countries and properties.
2) Search Partners: These are sites that are not Google's primary search and include a combination of Google owned and non-Google owned sites. With search partners, your ads can show on sites from YouTube to Google Local to other search sites, directories, or pages related to a user's search.
Some campaigns perform poorly on search partners as these can be non-search sites where ads are triggered based on other information, such as products displayed by a directory site. Some campaigns do just fine with search partners. What is important is to understand how you are performing on Google Search vs Search Partners so you know when to take action.
If your Search Partner data is significantly worse than your Google Search data, you will see an alert on your dashboard lists those campaigns where search partner traffic performs significantly worse than Google Search.
Click on the View button to see the performance data. Examine how your Google Search vs Search Partner data is performing for that campaign before making a decision. If you want to disable the search partners, simply click the 'Disable Search Partners network' button.