Define STP and NTP

Hint: First we have to know that STP stands for Standard Temperature and Pressure. NTP stands for Normal Temperature and Pressure. STP value is important to physicists, chemists, engineers, and pilots and navigators. NTP is commonly used as a standard condition for testing and documentation of fan capacities.

Complete answer:
STP refers to nominal conditions in the atmosphere at sea level. Standard temperature is defined as \[{0^o}\]C, which translates to \[{32^o}\] Fahrenheit (\[{32^o}\] F) or \[273.15\]\[K\]. This is essentially the freezing point of pure water at sea level, in air at standard pressure. As per IUPAC, the STP value of temperature and pressure for gas is\[273.15\] \[K\] and \[0.987\]atm respectively.
NTP is defined as air at \[{20^o}\]C (\[293.15\]\[K\]) and \[1\] atm (\[101.325\] kPa). It means NTP is set at \[101.325\] kPa but uses 20°C as the temperature. Many old books and online sources say that standard pressure is \[101.325\] kPa (the old IUPAC standard), but the current IUPAC standard of \[100\] kPa.

Additional information: A thermometer is a device used for measuring temperature. A barometer is a device used to measure atmospheric pressure, also called barometric pressure.

Note:
Mercury and Bromine only two elements are liquid at standard conditions for temperature and pressure. The gaseous elements Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine and noble gases Helium, Neon, Argon, Krypton, Xenon, Radon are gases at standard temperature and pressure (STP). Also, note that \[1\,atm = 1.013\;bar\], \[1\,atm = 76.0\;cm\] and \[1\,atm = 0.76\;m\].