A long-tail keyword is a specific phrase used to target niche market areas that are less competitive. It is defined as a keyword phrase with 3 or more words. It’s important to include long-tail keywords in your account as they help to achieve lower overall costs per click, and highly targeted traffic to your web pages.
Say you own an online shoe store: rather than bidding on the generic and highly competitive term ‘shoes,’ you can build out ads for specific styles or brands of shoes, say, size 7 black pumps. These type of terms are much more specific and less competitive to bid on.