This achievement requires you to eat 100 roots, across all games you play.
First let me start off by saying a root is the bush that can be found around the map. Roots are not to be confused with the berries, which don't have any leaves on it.
Similar to berries, roots (aka herbs), spawn in groups of 3-5. Per every 1 bush, the player will recieve 1 root, which will be dropped on the ground. Once you've picked up the herb, you have to consume it using
for the progress to go up. Again, the progress isn't for harvesting it, it's for eating it. That being said, using three to craft a First Aid Kit, then using the First Aid Kit DOES NOT count.
If you wish to harvest them faster, using 1 wood + 1 stone, you can craft a sickle. The sickle allows you to harvest roots and berries are an accelerated pace.
Note: Consuming a root grants the player some extra health!