No one has ever explained properly what it is.
GitHub is a freemium service for git repositories, which is now owned by Microsoft. There's a Wikipedia article about it. GitHub is probably the most used git provider, and especially many FOSS projects choose it for the community.
No one has ever explained what it does.
It lets you create git repositories in private or public mode (visible to others) and offers a few nice management features, like pull requests, task boards, issues, Wiki, project overviews, team management, etc.
Also it looks pretty complicated to set up.
Just enter a username and email and you can use it (aka store your repositories on GitHub as opposed to a different provider or your own git server). Many pages, like Hashnode, offer you to authenticate using the GitHub account, which means fewer passwords to remember and less typing, if you are logged-in to GitHub all day anyway. If you don't like GitHub, there are other services, too. For example GitLab, Bitbucket, Azure Repos, ...
Can any of you sharp minded people help me out?
For my sharp mind, your complaints sound more like you don't know git - or code versioning - than GitHub. Am I right? I recommend reading articles by industry leaders, like Atlassian (e.g. this one). Alternatively, I can summarize it for you.
If you have further, more concrete questions, just reply below!