so the way public transport generally works —in sweden at least— is that the bulk of it is managed by the regional government and uses a zone system (like the oyster cards in london i think). Then ontop of that there's SJ, the national train operator, which has its own generally separate ticket system that is more traditional where you book a specific departure between two stations.

Then outside of this you also have fully private public transport companies, of which the major ones are VR trains between stockholm-gothenburg, snälltåget which runs night trains from the north to south (sometimes down to hamburg/berlin), and flixbus which runs a bunch of routes throughout sweden.

so the strange thing about flixbus is that it runs a bunch of routes that take you between the same places as the trains can, in a less comfortable vehicle, and absolutely fucking hilariously slower.
For example gothenburg-stockholm is 3-4 hours by train and flixbus takes 6-7 hours.

There are some reasons i can see to opt for flixbus, most obvious being that it does serve places where getting to the trains is otherwise inconvenient and it can be like half the price, but it still astonishes me that a completely for-profit company finds that a sensible thing to operate here.