Quality score is a metrice attached to your keywords in your campaigns from 1 to 10 indicating how well your keywords match to users search terms that they type into the search engine
Quality score is made up with 3 factors
1- Expected click through rate
2- Ad relevance
3- Landing page experience
Expected click through rate and Ad relevance
These 2 factors are linked together.
Relevance of your ad to the users search terms is a direct factor of quality score .Also relevance of your ad is directly proportional to the Expected click through rate.More relevant yout ad to the users search term will get you higher click through rate.Finally leading to higher quality scores
Landing page experience
Lp experience is determined by several factors like
Your Landing page content should be unique if your landing page content is duplicated across the web and even duplicated within your website can negatively impact your Quality score.
Also your website has to be very easy to navigate.users should be able to find anything they need by one click without delay and any complications.
Make sure to include your keywords within your landing page copy make it more relevant
Highlight unique sale points throughout the landing page.Write unique copy for product descriptions and details mentioning specialities of your product rather than a generic description.