What are Marvel's .1 comics?

I've got a Marvel Comics app on my iPhone, I just opened it today to look at the new issues. There's a lot of new issues numbered with a .1, like "Deadpool 33.1", "Avengers 12.1" and "Hulk 30.1". What's that about? Appreciate any info. Phone Post

Self contained stories meant to draw in new readers but also set up the next story arc for those that read those titles.