The footer is the section at the bottom of every page on your site.
It used to display your contact information that your readers can use to reach you off the blog.
To edit, go to DASHBOARD > APPEARANCE > CUSTOMIZE > GENERAL OPTIONS > FOOTER SECTIONS.
You can change the icons or leave them as they are.
For the email and phone number sections, leave the code intact and only replace the email address (firstname.lastname@example.org) and numbers ((800)555-1212). Notice that you’ll have to replace the email and numbers twice within the code.
There’s also Footer Area 1,2 and 3 under General Options which you can use to display widgets. More on that here.