I can't think of a good way to put it without just giving examples, so here goes:

    1.0 = 100% usage of a 1-core system
    1.0 = 50% usage of a 2-core system
    4.0 = 50% usage of an 8-core system
    8.0 = 100% usage of an 8-core system

And IIRC, load average is represented usually as 3 numbers, which are over the last 5, 10, and 15 minutes.