The Customizer allows you to manage general styling for your entire website. This includes your site logo, icon, header, footer, etc. See instruction below for editing these sections.
You can set site identities like Logo, Site Title, and Tagline, Site Icon with this setting. You can find the setting under Appearance > Customize > Site Identity.
You can select a logo image from Media Library from logo option.
Astra allows you to add retina logo to the header from Retina Logo option. This 2x sized logo is necessary on high definition screens so the logo won’t look blurred.
It’s a small image icon that can be seen in the tab of a web browser, bookmark bars, and within the WordPress mobile apps. You can set it with site icon option.