An alias is a URL path that is used to refer to a specific page or content item in Drupal. It is a way to make a page easier to remember and access. Aliases are also known as "friendly URLs" or "clean URLs".

In Drupal, aliases are created and managed through the Pathauto module. This module allows you to create custom aliases for each page or content item. It also allows you to set up patterns for automatically generating aliases for new content. For example, you can set up a pattern that will automatically generate an alias for a new blog post based on the title of the post.

Aliases are important for SEO (Search Engine Optimization) because they make it easier for search engines to find and index your content. They also make it easier for users to remember and access your content. For example, a user may remember the URL of a page more easily if it is a short and descriptive alias instead of a long and complicated URL.

In summary, aliases are a way to make URLs easier to remember and access, and they are important for SEO. The Pathauto module in Drupal makes it easy to create and manage aliases for your content.