Handiwork is something that you've done, achieved, or made, especially with your own two hands. When you hold up a pair of mittens you just finished knitting, you're admiring your handiwork.
You can use the noun handiwork for the result of hard work, like a tidy, weeded and mulched garden or a handmade birdhouse. You can also look at something less positive, like a messy living room scattered with books that have been pulled from the shelves, and say to your two year-old cousin, "Is this your handiwork?" This word comes from the Old English handgeweorc, from hand and geweorc, "work."