Focus Flights are specific services that BA is particularly keen to operate as punctually as possible, whether it be because of high volumes of connecting passengers or recent poor performance.

Not long ago, I saw a little notice about some LGW-AMS services - one of which was scheduled to arrive close to the noise restriction limits in AMS, and another service that had been consistently unpunctual and was in danger of losing it's slot!

I'm sure someone can post a more substantial answer, but that's the basic gist.