Roitman's Principle Delta

In this talk we present  Roitman's principle Delta which is a combinatorial statement introduced to prove `the normality of the countable box product of the convergent sequence' (this is the box products problem and is probably the oldest open problem in general topology). The principle Delta is known to hold in many models of ZFC and it is unknown if there is a model where it fails. We will focus on its set theoretical aspect with a topological flavor at the end.