An email list is a list of email addresses of subscribers or prospects who have given their consent to receive periodical information from you in the form of newsletters, Webinar registration forms, product pros and cons, new product launch news and so on.  These email addresses must be collected by you via capture forms embedded on to your landing page.  Building an email list is crucial when it comes to marketing your product or service through the method of email marketing.  You can always take the help of an email marketing software to start collecting emails from the visitors on your business website.