The first report you need to check in Google analytics is “source/ medium report”. This report includes useful data about the source of the traffic. from which source traffic is generated on your website such as ( Google organic, Google paid, Facebook, etc ) and the medium of the traffic such as (search ads, display ads, banner ads, email, etc.)
You can find Source/medium report under the Acquisition > All Traffic menu
Want to learn complete Google Analytics Tracking? Join Google Analytics Training Course Now