Fuel Gauge issue
 

2011 Silverado 5.3 L, Z71, 36000 miles.
Hi, brand new to this forum but not forums in general. I bought this truck 3 years ago, "certified, Pre-owned" off lease. Love the truck and had no issues til now.
I'm starting to see an issue with my fuel gauge. At first, it worked normally but now it seems to be heading toward empty much faster with each tank of gas. I thought the mileage was decreasing but after doing the math, it's still the same. Some posts here lead me to believe that the sender in the tank is going bad. But in one post someone mentioned a fuel "sensor". My questions are

1. Is there such a thing as a "fuel sensor" that might be improperly working?

2. If you think it's the sending unit in the tank, what's the right one to replace it with? OEM / GM sender or aftermarket?
Thanks for the input.