Usually, when someone says "integrally suppressed" it means that the suppressor is made from the barrel, not attached to the barrel.
Its still a tube within a tube design, but the inner tube is the barrel itself. Advantages? No big, long, heavy thing hanging off the end of the barrel.
Disadvantages? its permanent (short of swapping out the barrel), so you no longer have the option of suppressed or non suppressed.
Also, I don't know how well it would work with multiple holes in the barrel itself, in high pressure rounds like .223 and .308.
Doing that with a Ruger 10/22 is one thing, doing it with a larger caliber might have issues I'm not familiar with.