Dominios (Domains) is the screen where you register your organization's own domain or subdomain (for example donate.myorganization.org) so your landing pages are published with that address, instead of the default AFRUS address (web.afrus.org).
As the screen itself says, linking your own domain makes your landing pages show your organization's URL, strengthening your brand and building more trust in your campaigns.
In Fundraising > Dominios. Labels are shown as they appear in the Spanish version of the console. There you add domains and see your Lista de dominios (Domain list), with each one's Status (active or inactive), Versión, registration Fecha (date) and how many Páginas (landings) use it.
No. You buy it from a provider (GoDaddy, Media Temple or another) and set it up there.