In SharePoint, you may have the ability to share a file with others. In others words, you would be giving access to others at the level of access, view, or edit, that you choose, but you might not have the ability to remove or edit that access once set. Depending on the way your organization set up your account, you may also have the ability to give access to others outside of your organization.
File sharing is not a best practice and should be used with care. See the warning about The Danger of the Share Button in Chapter 16, More on Using SharePoint.