Google can show your search campaigns across two different areas.
1) Google Search: These are Google Search owned properties such as Google.com, Google.fr, and so forth for various countries and properties.
2) Search Partners: These are sites that are not Google 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 upon 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:
Just click the alert and you'll be taken to the screen where only relevant campaigns will be filtered out.
Click on the red exclamation mark icon and open the campaign settings and 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, just click the 'Disable Search Partners network' button, and this will disable Search Partners from showing ads from that campaign.