switch { } need help

So if I have:

(indulge me)

switch j
{
    case 1:
    // blah 1

    case 2:
    // blah 2

    case 3:
    // blah 3

}

and j = 1, if there is no break after each of the blah things, why/how would blah 2 and 3 be executed?

I can understand (not really) that break; stops the program continuing to look for cases where it matches
and so "saves time", but is there more to this than I am seeing?