Trigger words are the words and phrases that trigger a user into clicking. If the user is looking for 'pricing', and your link says 'pricing', they're going to click on it. So in this case 'pricing' would be the trigger word.
Remember, people spend lots of time on many websites and are familiar with certain terminology - don't try and reinvent the wheel as it may just confuse your audience.
Determine what your tigger words may be and we'll put them to the test in the next task.