What does "Up to 8 weeks of color!" mean for hair dye?

I quickly bought a box of hair dye, (I was in a hurry) and I got home and read the box, and saw it said "Up to 8 weeks of color!". Does this mean it's semi-permanent dye, or are they saying I'm going to need to redye my hair in 8 weeks? If I use this in my hair, is it going to fade right out, or no? Is what I'm trying to say here.