YouTube Studio is a product of YouTube, itself a division of Alphabet, the company that most people know as Google. It is available for people who have videos on YouTube both as a link from the main YouTube page, and as a separate app on mobile phones.
Now the sweetly naive might be thinking "Studio? This must be some type of product that allows people to make and edit video content!". Oh, you sweet summer child. With the exception of facial blur, subtitles, and placing information cards, I don't think there is currently a way to change the appearance of a video in YouTube Studio. In reality, "YouTube Studio" is a gigantic package of data and statistics that cover every aspect of the who, when, where and "how much" of how videos get watched. YouTube is a Google product, and so the amount of data that is collected and shared is massive and labyrinthine. For every video I have on YouTube, I have a graph of the views, watch time, and subscribers it has gained over time. I also have a separate graph of audience retention, showing at each second of the video how many people are still watching it. I also have a breakdown of how people found the video, whether through "Browse" mode, search mode, or external links. For external visitors for a video, I then have a breakdown of what websites the links came from. For search terms, I have a breakdown of what the search terms that led to the video were. I also have demographic breakdowns for each video: I can tell the age, gender and nationality of viewers. I can also see this data, and other data, in the aggregate. I can search the Operating System of my viewers, for example, and find out that Android users watch my videos for an average of 1:15, while Roku users watch my video for an average of 3:51 (which makes sense). There is even an "inspiration" tab that shows what other subjects that people watch my video might also be interested in. There are so many tabs and information that I sometimes forget where something is located.
There might be several questions about this. The first might be about privacy. Does this mean that each time you watch a video, the person who posted that video knows your personal information, location, and what you were searching for? Well, while Google might know those things, people posting videos don't. The demographic information and search information have to reach a certain level of aggregate before they are displayed to video creators. Even then, the information is generally very vague, and perhaps inaccurate: according to YouTube, of the almost 12,000 people who have watched my most popular video, about Arcata, California, 0% were under the age of 45. The search terms are also not shown until they have reached a certain number, and even then are usually pretty vague or obvious. The number one search term for my video about Arcata is... "Arcata, California". So from a privacy point of view, the circumstances where a creator would know anything personal about their viewers would not normally occur.
The second question might be, does all this analytical micromanaging ruin creativity? And that question is harder to answer. Seeing what points in my video are drop-offs has certainly changed how I make videos, especially in terms of length. I don't think this is all bad: it has made me edit out some rambling and pointless shaky cam shots. I also try to make my video titles and descriptions include keywords that people might be searching for. This is also not bad. "Hood River, Oregon" makes a better video title to search for than "Wow this was such a pretty river I had a great time!!!!!". I also can now test thumbnails, and know what type of shots are engaging and honest for an audience to click on. All of this is pretty useful. But it can also lead to a monoculture on YouTube, where videos tend to start being the same length and format. This isn't by accident: all those creators are watching those graphs, know where the audience leaves, and are adjusting their videos to be snappy and have hooks to keep you there. Remember last year when so many videos had thumbnails of the creator's surprised face over a written expression of disbelief? That trend was for a reason. How much analytics changing creative endeavors is a good or bad thing is a complicated issue, so I will just say that for me personally, the analytics of YouTube Studio have mostly managed to have me trim the fat, but I can certainly see how it could have unintended consequences.