The tarsometatarsus is a part of a bird's leg that is kinda like its ankle and foot all squished together into one bone. You know how you have an ankle bone and then a bunch of bones in your foot? Well, birds are different and they evolved to have one big bone that does the job of both of those things.
So, the tarsometatarsus is really important because it helps a bird to stand on its two feet and walk or hop around. It's also really strong because it has to support the weight of a whole bird! And some birds, like chickens or turkeys, people like to eat their meat, so the tarsometatarsus is an important part of that too.
Basically, think of the tarsometatarsus as a special bone that helps birds stand up and walk around. And it's really tough!