Math Template - what is this?

[spiff72]

Just messing around with the calculator after receiving it 2 days ago...

There is a template that I am not familiar with in the top row of the templates, third from left (between the exponent and derivative). It looks like a vertical bar with two entry items offset vertically. It's been almost 30 years since I took calculus classes, and this one struck me as unfamiliar.

Can someone tell me what this one is? I tried the help function but it just gave general info on the template button.