What exactly does this mean as well for I was using someone else's code...
I would suggest that you look at the reference page, and add some Serial.print() statements to work that out for yourself. You will remember for far longer than if we explain.
The key parts are the bit shift (>>) and the and (&). The bit shift is moving the position of the 1 around in the constant. That new value is then anded with the number you want to display. It is, effectively, forming a mask. When the particular bit in number matches the shuffled around bit in the mask, the masked value is shifted out, lighting one segment of the 7 segment display.
Since the loop loops 7 times, each of the 7 segments may, or may not be, lit, depending on what the bit pattern in number is.
If number is 0b01100000, you can see that two bits are true, so, the loop should call shiftIt() twice, to light 2 of the segments. If the correct pins of the 7 segment display are connected to the correct Arduino pins, the 2 segments that light up should be the 2 segments on the right side of the display, forming a 1.