With spaces you can sort your topics and projects correctly. You can have a personal space, global spaces and page spaces. Depending on your needs, you can split them into topics, which are relevant for your company. You can create as much spaces as you want. For example you could create a space for your marketing department, in which you can discuss internal stuff or attach your price lists. The other spaces would then be HR, Product Management, etc. Each space can hold an unlimited amount of pages (and blogs) with a customized structure.
You can keep a space private so that you will be the only one who can see it (that's usually the case with personal spaces), or you can set different permissions. If so, the space is only visible/editable to some specific groups of your company. You can even publish it like a normal website and make it visible to everybody.
This means spaces are used to structure your info and you decide who can access and/or edit them.
Here you can find more information about spaces: https://confluence.atlassian.com/doc/spaces-139459.html
If you have further questions, just let us know.