SharePoint Online has been rebranded as Office 365 and its in public beta.. You can signup from here and get the account and try it out by yourself…
http://www.microsoft.com/en-us/office365/online-software.aspx
It is not for install, think about it as SharePoint in the Cloud.
BTW – There are other providers that host SharePoint in the cloud and therefore offer “SharePoint Online” but Office 365 (formerly BPOS) is hosted by Microsoft.
And see video on Channel 9