No. Only the video of the instance you are visiting, and the ones on instances that are followed by it.
The project lies at joinpeertube.org, but there is no one gateway or instance representing the network. Each server running PeerTube has its own view, more or less complete depending on the instances they follow.
The difference between Peertube and other services like youtube, is that Peertube is decentralized and federated.
There is not only one Peertube, they are hundreds instances.
Each instance can choose to «federate» or not with some/all others. When an instance «follow» another, it means that you will be able to find the videos of the second one on this instance.
Some instances try to federate with all others. On these instances, you will be able to find all videos, like on youtube for example.
Other instances are thematic, or standalone.
More explanations here: JoinPeerTube (read the entire page to get a better view of what is Peertube).