With other words: the anatomy of the SharePoint2019Commands PowerShell module.
There are a couple of technologies out there in the world which implemented support for PowerShell but not with modules, instead they went with the more traditional Snap-ins. One of them - probably the most famous one - is SharePoint Server. The snap-in used by SharePoint is called
Microsoft.SharePoint.PowerShell and many SharePoint administrators have had unpleasant experience using it.
The challenge of snap-ins comes from the fact that they don't offer autoloading like how modules do since Windows PowerShell v3. which means every time we forget to run
Add-PSSnapin we risk running into a Command not found exception.
The solution is to wrap the snap-in in question into a module and expose the commands in the module manifest, so the engine of Windows PowerShell can find the module and load it for us.
Now I'm going to stop typing, so the video below can tell you everything.