A stopover is the time period between two consecutive flights above a certain duration and is typically used for a multi-day period. So, say you’re flying from London to Miami and want to spend a few days in New York, you would book a flight with a stopover in New York.
A layover is a connection between two consecutive flights that doesn’t count as a stopover. Typically this is under 4 hours for a domestic connection and 24 hours for an international connection.
You can’t have a stopover or layover on a non-stop flight, but you can on a so-called direct flight. A direct flight is one or more flights that do not change flight number between the consecutive flights, even if you change aircraft and can even miss the next part of your flight!
The rules of any fare dictate whether a stopover is allowed and if so, how much it costs. By adding in a stopover it could add a fixed fee, say $100, or be disallowed and force an extra fare component requirement. This could involve a significant cost increase.
Credit:stackoverflow.com‘