A Campaign is a set of emails you send to your prospects or customers
An email campaign is a series of emails (steps) a business uses to communicate with customers or prospects. They are used to persuade customers to engage with the company (download a white paper, sign up for a webinar or your service, make a purchase with a provided coupon, etc.).
Each campaign should include a certain number of leads (your current customers or prospects, ie., email recipients).
Each campaign has a number of settings (email account used to send email from, maximum number of emails sent per day, your email signature/footer, etc.).