Commercial Social Networks are accessed either through their own app, or a web page. In either case they exist as an island, although a giant one, accessible only to its inhabitants. If you want to visit these, beyond a teaser glimpse, you have to create an account, allowing them to claim large population and influence, and data to sell to the advertisers who fund them.
They are also designed to be addictive, the algorithms which select the content you see will show you more of what you are interested in – which sounds good. For people with, for example body image problems, this tends to lead
There are also a large number of much smaller islands, which welcome visitors. You do not need to provide any form of identification – such as creating an account to look around, though you will need an account somewhere on this network of sovereign areas to follow or comment. This collection of sites is also known as the Fediverse.
Being part of the Fediverse
If you run your own website you may be able to easily become one of those islands. If your website is based on WordPress there is a plugin (described here) you can use to put out new posts on your site as Fediverse status updates.
There are similar plugins for Drupal, etc.
Most of the Fediverse runs on dedicated server software, Mastodon or Pleroma, or a host of others. which require knowledge and money (not necessarily a lot) to run. You can probably find a server you can join which matches your interests, and if you try this route then contributing to their running costs will help to keep that server going.
Examples
Here are a random selection – well not really random – there is quite a lot of technical and bits on the Fediverse, written by technical people for other technical people, so these are less usual, but growing in number.
https://mastodonapp.uk/@uktw – UK Theatre Web
https://mastodon.social/@gutenberg_org – Project Gutenberg – if you are into books, so are they.
https://mastodon.scot/@scotlit – Association for Scottish Literature – -if you are into Scottish Books
https://mastodon.social/@onlmaps – interesting maps
https://mastodon.social/@medieval_illuminations – Medieval Illumination
Science
Fediscience is a social network for scientists. You will need an ORCID identifier to sign up. Interesting mix in the Profile Directory, climate science, transport, biology etc.