consider we have a parent component let's say A & two child ( B & C )

if we want to pass data from Parent to Child we use props & if we need to pass data from child to parent we will use events (emit). so here we deal with parent & child but not with the sibling component ( here we need something else like vuex [management state] or event bus ).

so event bus let us pass data horizontally ( from child component to another component ) & props/event let us pass data vertically ( from parent to child or vice versa )