Good question!
When you book a return fare - let's say from Sydney to London and back to Sydney - you'll be travelling with the same airline both ways. You'll be limited to the airlines schedule, and their routing.
Mixing & Matching your flights puts you in the drivers seat (not literally!) and lets you choose the airline, departure times and stopovers that work best for you.
Example:
Qantas Return: Sydney to London (via Dubai) and then London to Sydney (via Dubai)
Mix & Match: Sydney to London (via Hong Kong) with Cathay Pacific and London to Sydney (via Singapore) with Singapore Airlines
Benefits of Mix & Match:
- More Choice
- More flexibility
- More stopover opportunities (give yourself enough time during a stopover and explore the destination as a day trip - like Hong Kong and Singapore in the example above)