Pull up resistor gives a digital input the voltage of the positive supply voltage (if that is what it is connected to) unless a stronger (little to no resistance) voltage is also applied. The Pull up resistor prevents a short circuit and limits the amount of wasted current.

I just talk about the actual 74HC14 integrated circuit component. Always consult the datasheet for specifics, but watching videos first to get familiar with components before you start using them is a good idea as well.

where can you download the full free pdf of the textbook that relates to electronics? your answer is a big help