Why does some papers, after printing, the picture or the places with ink become smooth? -

In my school, when we get papers or something, the pictures which are usually black and white, come out smooth and we love to feel them cause they are so smooth. Please tell me why, if you know! I know this question is dumb, but I always wanted to know!

Because non-glossy paper is expanded (may not look like it but its huge lol) when the ink is applied it compresses it. Like a sponge when you squeeze it all the holes disappear and it looks smooth.

greasy ink ??

because the machine does something...

i thinks its because they have laser printers