The ‘craters’ in the ground- are they just decorative or Easter eggs???

What are these things? The reason you see a lot of dirt holes is because I dig those craters, and also those little grass sprout things and nothing pops up. I learned how to identify seeds and worms, because those are green or brown, wiggling things… But are these just like decorative patches of grass, or sprouts?

I’ve seen people trying to ask what these are, but they never really included a picture, so I hope this visual helps.

Backstory, I downloaded the game for the first time three days ago, and I am learning and exploring as I go. The farm type that I chose was the river land to start off.