AVcc, Aref, and the GND pin near them are applicable to the analog inputs (that GND pin is sometimes referred to as "AGND"). The Vcc and GND on the other side of the chip are applicable to the digital inputs. In an ideal
design those analog and digital GND connections would only intermingle right at the power jack. All of your analog pins would only use their AGND and be kept separate from the GND used by the digital pins. There would be three separate capacitors between AVcc and AGND, Aref and the same AGND, and Vcc and its associated GND.
As an example for why all this is, when you're blinking your LED on pin 7 and it's jumping between 5V and 0V you're causing small voltage surges/drops that can be noticeable by the analog pins. Normally the analog pins will only see slow changes in voltage around them -- which is great for stable readings -- so you don't want to introduce additional noise from your blinking LED.
You really only do most of this stuff if you're really concerned about getting the most stable analog readings possible and for most projects it doesn't matter. The official Uno doesn't even follow these rules. But, you asked, so I did my best at explaining