The search network is a network of several search engines on which you can run your text based ads. Google is the primary one, but there is also AOL and other additional search engines. Your ads are triggered and shown on the search results page once a Google search user searches for search terms that your keywords target. This means, you target users who are potentially already interested in your offer.
The display network is Google’s huge network of millions of websites that use Google AdSense. On these external website your ads can be displayed, including image ads and other formats.
Your ads run on websites that are relevant to your ad and vice versa, based on different targeting methods such as keywords, placements and other options.
Decide on where to run your ads based on your specific marketing goals. The search network can be used for a very targeted sales approach. While the display network is recommended if you want to raise awareness for your brand across a larger reach and aim for a wider exposure.