Text ads are make of four components; headline,description line,display url and final url.
Text ads must be clear, concise and accurate, avoid phone number and limit the excessive use of exclamation points.
If you have more than one ad per ad group, google will most often show the ad with the best performance.
The landing page should match your keywords and ads.
If the user is on a mobile device, your landing page should work well on it.
Call-only ads allow you to receive calls from mobile devices and track the calls.
Product listing ads are useful for selling products.