Google Video, when it was originally introduced, was a competitor to YouTube that let you upload videos and either offer them for free or charge users to view them. If you wanted to view a video you purchased, you had to download the Google Video Player to see it.
The service was not a big hit, Google ended up buying YouTube, and they eventually shut off the ability to charge for videos. Google Video began to be converted into a search engine for video files rather than a place to distribute them. Anyone who had ever purchased a video from Google Video was offered a refund.
In 2011, Google further dismantled Google Video and even videos that had been previously uploaded to the service and available for free viewing were removed. Users were given advance notice in order to transfer the videos to YouTube or download the uploaded file. Google Video officially ceased to exist as anything other than a search engine.
Originally YouTube was a free model, and Google Video allowed content producers to set a price. Now rentals have come to YouTube.