Critical Realism is a philosophical position (with many forms within different disciplines) which affirms that reality can be known, but only through a critical process. It gives way neither to thoroughgoing skepticism or naive realism, but affirms the real and our capability to come to a grasp of it.
Skepticism (phenomenalism) denies that what is known refers in some way to reality.
Naive realism claims that knowing is something like seeing, that the real is what is out there now, immediately accessible to the senses.
Critical realism over and against both, understands knowledge to be the result of a process. Reality is neither completely shrouded nor easily accessible. The world we live in is a world mediated by meaning, and knowing it requires an active engagement with it, an attentiveness and a drive to know.
