Question

what is the difference btw decomposition and displacement reaction'

Answer 1

hii bae...

Decomposition reaction is the process in which substances decomposes to form new things 
On the other hand 
In desplacement reaction one element desplacea another element

I hope it will help u

Answer 2

decomposition reaction is a reaction in which one compound breaks into two or more compounds
whereas is displacement reaction is that in which a highly reactive element displaces a weak reactive element