Hello I have 2 questions regatding physics chapter on Mechanics I

1 - In one of the Q. The maximum force of static friction is 400N for a crate but if you push on it with a force of 250N than the static friction will be 250N. The princeton book says...imagine if you push on the crate with 250N of force and the floor pushed it back with 400N of force. So my confusion is that the floor's force is an upward force called normal force and its a perpendicular force, whereas the static friction force is a parallel force. So how come we are defining static friction force as normal force?