How to manage Site Title, Logo, Tagline and Site Icon?

1. From Customize section, go to Site Identity.
2. From Site Identity, you will be able to add various options related to site identity like:

Logo ( Only available in WordPress versions greater than or equal to 4.5 ): It changes the main logo of the site.
Site Title: It changes the main site title of the site.
Tagline: It changes the tagline (i.e: Description) of the site.Just below the site title.
Site Icon: The Site Icon is used as a browser and app icon for your site. The icon must be square, and at least 512px wide and tall.