No kidding, and it's been explained multiple times in this thread.

Non-rev: You are using travel benefits on your airline/your parent airline(s). You are not run through CASS, you are purely waiting to make sure there are enough seats for you and possibly your companions. This is a benefit as part of your employment, and basically at the discretion of the gate agent having enough time to clear you and give you a seat. No need to be in uniform or even show that you're an employee of said airline. You do not need to check in with the captain or crew.

Jumpseater: You are not using travel benefits on your airline or parent airline. You are attempting to ride as an additional crewmember. Depending on load and company, you may be run through CASS. If a seat is available in the back, you will be placed there. If not, you may be allowed to ride in a cockpit jumpseat (or FA jumpseat on some airlines, I believe). Either way, you riding is at the captain's discretion, and checking in IS required.