The specifications for the new Edexcel science subjects state that How Science Works (HSW) is a newly introduced section of the GCE Science criteria, that builds on from the Key Stage 4 Programme of Study for science. The concept of HSW isn't quite new however, it's just that HSW now plays a major role in testing students' scientific knowledge.
So what does "how science works" actually mean? In addition to teaching the "facts" of science, teachers are now required to teach students things like "there are some questions that science cannot currently answer, and some that science cannot address", and that scientific and technological developments have their "benefits, drawbacks and risks".