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

https://channel9.msdn.com/posts/Office-365-The-power-to-think-big-and-be-small-to-be-big-and-act-fast