Google userId vs.userProfileId

Question

What is the difference between the userId and the userProfileId that the following URL returns? http://www.google.com/reader/api/0/user-info

(sign-in to google required to see the json results from the above URL")

Answer 1

The userId seems to be the ID of your google reader account.
While userProfileId is the ID of your Google Plus Account

So, you would access all items in your Google Reader Account with: http://www.google.com/reader/view/#stream/user/{UID}/state/com.google/reading-list.

Your Google Plus account would be at: https://plus.google.com/{userProfileId}