Booking flights on separate tickets means buying two legs from airlines that don't talk to each other, then stitching them into one trip yourself. It's often cheaper than the single through-fare, sometimes by a lot. The catch is that the airlines never agreed to connect you, so if the first flight is late, the second one leaves without you and owes you nothing.
That's the whole trade. You're swapping a lower price for the protection a real connection gives you for free.
What you give up
On a single ticket, the connection is the airline's problem. Miss it because the inbound was delayed, and they rebook you, usually at no cost, sometimes with a meal or a hotel if you're stuck overnight. Your bags get checked through to the end.
Separate tickets throw all of that out. Each airline sees its own flight and nothing else. If leg one lands late and you miss leg two, the second airline treats you as a no-show. You buy a new ticket at the walk-up price, which is the most expensive fare on the board. You also collect your bags after the first flight and recheck them yourself, which eats time you may not have.
When booking flights on separate tickets is worth it
It can still be the right call. The savings have to be big enough to cover a missed connection and then some, because that's the downside you're insuring against yourself. Give yourself a real buffer between flights: a few hours, not fifty minutes, and more if you're switching airports or clearing customs in between. Fly the risky leg early in the day so there's another flight left to recover on if things slip.
This is a close cousin to skiplagging and the math behind what a layover is actually worth: a cheaper number on paper that comes with strings, and the strings are yours to manage.
What we deliberately don't do
We don't stitch separate tickets together and sell them to you as one smooth itinerary with a scary-short connection buried in the middle. When the three fares we send each morning include a connection, it's one the airline actually stands behind. If a separate-ticket play is worth the gamble on your route, that's a call you make on purpose, with the buffer and the backup flight in view, not one we make for you by hiding the seam.