It's very common to use resistors to pull them up to high logic, which is 5 volts in this system. It's just as possible to have a pull down resistor to ground. I'll get into that more in a latter experiment. Buffers are used to increase the output drive capability of a line, or to lighten the load seen by outside circuits. 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. When one is turned on, its normally pulled-up input is pulled down to ground. That information is considered in the buffer and can be read out of it. All of the above, but the most accurate would be that it is a place where a closure device can be connected. I am currently working on the 64 switch matrix program and circuit.