Some return trips consist of two single tickets, giving you the lowest possible price. If you have two single tickets, this will be indicated on your booking as a “One-way combination.”
You travel the way you normally would on these tickets, however, if there are any changes to one or both of the tickets, note the following:
Even if the stages are booked together, they are treated individually. This means that each stage of your journey is handled separately in the event of cancellations, alterations, traffic disruption such as strikes, and timetable changes. Each airline's regulations will apply.
If one of your flights is changed or cancelled, this does not affect the other flight. But the regulations and limitations to your options for changing or cancelling your booking still apply to the other flight.
If you want to cancel the whole trip you have to cancel both tickets individually.
There may be different regulations regarding baggage; check the website of each of the airlines you’re flying with.