Dumb Question: Tires

Dammit Jim, I'm a computer geek, not a mechanic.

That said, I'm wondering what the real difference between "LT" and
"standard" tires is with respect to tires on an SUV. I realize that LT
stands for "Light Truck," but when shopping for tires for my wife's SUV, I
find many varieties of tires of the same size, some of which are rated "LT."

Does it matter which ones to get? What are the pros & cons?