difference between molecularity and molality ?

Hi Student
Is that molecularity or molarity?
Anyways Molecularity is the number of atoms, ions or molecules that must collide with one another simultaneously so as to result into a chemical reaction.
Molality is different thing.
You can study about molality and molarity, their relationship and much more on the given link
http://www.askiitians.com/iit-jee-solutions/methods-of-expressing-the-concentration-of-a-solution/