Whats does screen do in media query? why even type it?

I don't notice any difference in writing screen and omitting it. For example:

body { background-color: lightgreen; }

@media (max-width: 900px) {
    body {
        background-color: pink;
    }
}

body { background-color: lightgreen; }

@media screen and (max-width: 900px) {
    body {
        background-color: pink;
    }
}

is there any difference between these two codes?