Drupal includes a module called Media - for most sites, you'll turn it on and use it to place images, videos, documents, and then when you're actually using all of those resources on your site, you'll find that with images, you can create the Alt text once and it's just automatically there when you use that image. 

You can also create Views directly with media rather than putting the media objects in a content type (e.g. a gallery of images or videos) using just the Media, with in this case, a Taxonomy field added on to filter and group the videos. 

Domain names are structured with the protocol (HTTPS:) // domain-name . top level domain (.com, .org, .ca). Anything between the separator for the protocol and the domain is a sub-domain. 

You register your domain name with a registrar that has the authority to add records to the TLD, so it is unique in the world to create URLs that point to only your web services (Unique Resource Locator). If you have multiple resources using the same domain, you will use subdomain names (also unique within your domain). 

Subscribe with a SaaS provider

There are now a few very good options for using CiviCRM without managing a Drupal site or server at all - Spark (CiviCRM.org's own starter service); CiviPlus (from Compuco); Civi-Go: CiviCRM SaaS Hosting (by Ixiam). 

There are a lot of resources to learn Drupal, with a wide range of prices and time commitment. 

The first step for everyone should be to create an account on Drupal.org (and optionally -- but highly recommended -- join the Drupal Association). 

If you're responsible for maintaining sites, you should add a subscription to the Drupal security newsletter (you'll get notices every Wednesday of security issues with Drupal core and modules). Even if you're not doing the maintenance, you can be aware of what issues are being fixed.