I’m posting this as a trick question brain teaser.
Pictured is the base of a cherry tree (Prunus avium). Please vote if you think this is a grafted tree or an own root tree. Feel free to explain your reason for thinking one way or the other. I will reveal the answer later in the comments. 
I vote grafted although I have seen a loot of ungrafted trees with a similar sudden bark change and enlargement at Cincinnati’s Spring grove cemetery. These trees. Since your tree is a cherry tree and if it is a fruiting variety It would likely be grafted.
I’m guessing own root because you said it is a trick question and there is an obvious change in bark there.
I could add further conjecture but I’m not sure if you want people to vote free from further influence from me
Or is the trick that it looks grafted, but I make people second guess their confidence even if it really is?
My lapins cherry is grafted and it is not obvious. I may have burried the union in landscape mulch.
My CHE is grafted to Osage Orange and it is obvious… completely different bark and the OO has outgrown the CHE diameter wise.
Just going on looks I would sure think yours is grafted.
TNHunter
I’m on the grafted side. Drastic change in bark and size both had to be caused by something, and that’s the only thing I know of that could do both at the same time.
Alternatively, could some kind of girdling have caused it in a non-grafted tree? Seems unlikely, but what do I know?
I guess there could be some kind of root disease that made the root crown look weird, but I’m going with grafted, too
That’s a good guess. I can’t guarantee there is no disease at play here, but I’ve never seen any obvious health issues with this tree or its neighbors.
Is it a tree growing up through the trunk of a previous tree?
That’s a good guess, but it is actually all part of the same tree. I’ll give another hint. There are multiple cherry trees growing in close proximity and while the change in bark at the base is especially visible on this one, many of the others show a similar look even if less pronounced.
Meandering Root ball sucker then?
It kind of has that “cruddy bark” look that american chestnuts can get as a response to fighting against the fungal blight.
I’ll guess grafted since it’s a cherry tree. And wondering if that’s from burrowing insects or just stress where the tree releases the jelly like my Almond tree did from fungus or watering in hot day temps and cold nights.
But what’s really going on with that tree trunk in the background?
Good eye. Assuming you’re referring to the split trunk tree in the background, that is also a cherry tree.
Result of forest fire ?
I’ve seen no evidence of fire in the area except on a couple of old tree stumps which were cut down many decades ago and seem to be from a time before these cherries existed on the site.
Yes that’s what got me thinking about those issues. But after reading a couple above it would make sense that the rootstock has that different bark. Although there’s still something going on that other split tree 
Is it a graft of itself on its own roots? A prunus avium stump that was grafted with prunus avium?
I’m hoping for more people to guess before I give the answer as to whether or not it’s grafted, but I will confirm that the roots and top are all Prunus avium with no other species involved.
The other trees in the background appear to have the same characteristics. Looks like mechanical damage to me, maybe goats, sheep or hog?
Prayers and support to all families affected by hurricane helene.
