Breaking compatible trees with an axe will cause connected valid blocks to be destroyed, creating a "tree feller" effect. Each block destroyed uses one durability on the axe, regardless of the unbreaking enchantment.
Felling a tree with Arborenda
Valid Blocks
Additionally, Wart Blocks, Shroomlights, and Mangrove Roots connected to logs are broken.
Technical Details
The connected blocks are broken in a width-first manner and the process can be terminated either
naturally: When the algorithm runs out of connected valid blocks, or
forcefully: When either 256 blocks have been destroyed, or 32 recursion layers have been exceeded.