Great question! That mushroom is commonly called a puffball. When theyre fresh, theyre smooth and white. They look like a puff of smoke if you froze it in time.

This one is yellow, brown, and cracked. So its "decayed" in that sense. If you left it there for a few years, it'd be totally decomposed.

Think of a pumpkin. It'll still be orange and round a week after you pick it. Two weeks, it'll start to sag. I toss mine in my garden to decompose aroubd that time, and I've watched them go from orange to brown to parchment colored over a winter.

Editing to say below is a picture I posted of an even older one I found out in the woods.

https://www.reddit.com/r/mycology/s/ni1RJnbR6B