Google analytics tools are great insights into the mind of your customers. We can't get feedback all the time from people that visit your website, but we can analyze their behavior. This can lead us to better being able to focus on what is the most needed thing to do at this time. You can know which pages are most engaging and which need some work.
Keywords take trial and error to know what will work best for your ad. Combining the keywords with the insight from website traffic can help determine if certain keywords are helping or hurting your business. Google is great to offer quality scores that give insight into how effective they feel your keywords will be for a given ad.
All in all these tools will help to build an engaging website if used frequently and diligently. Knowing the inner workings of your efforts will help to maintain and create a great pattern for building a strong business.