It actually performs no logic. It looks like an inverter without the bubble, and is called a buffer. It's a triangle with a single input and output. It is not used for logic, but to increase the output drive capability of a line, or to lighten the load seen by circuits outside of ours. This is sometimes called repowering.
Some buffers have a third line entering the side of the triangle.
When it is not activated, the output of the buffer is removed from the circuit to keep it from interfering with other devices. Combinations of on and off conditions are often important determinants of condition, and the use of logical combinations as outputs can be used to cause complex actions. To determine the result when logical operations are applied to larger variable types, simply work with one bit at a time. Some examples follow. The numbers are presented in both hexadecimal and binary form.