You can watch our Video #39 of the video tutorial series "Learn Atlassian Confluence" to learn about spaces.
A space is a place in your wiki, in which you can put related things, such as content, pages, and documents. Spaces provide you with the opportunity to collaborate on a project with your team or a group of people.
Each space has its own permissions, which assign administrator access or other privileges to individual users. You can create as many Confluence spaces as you want, and then archive or delete them later as needed.
There are two basic types of spaces:
The first type is the global space, those listed in the space directory. These are the spaces in which you create content and collaborate with others. These are also called site spaces.
The other type of space is the personal space. Each Confluence user can create their own personal space, either private or public. Your personal space is listed in your user profile and can be viewed by clicking on your profile picture.
You can also read more about spaces in Atlassian's documentation, starting on this page.