Engagement Rate refers to the percentage of people who engage with your social media content - either by likes, comments, or shares.
Click-through rates for social media refers to the number of followers who click a link on your social post that takes them to your website or blog.
Followers are social media users who have opted to receive your content on their timeline.
Impressions refers to how many times your posts showed up on a timeline or newsfeed. This KPI is calculated individually across platforms.