In the formula E = hf, what does h stand for?

Related questions

• Question #f2711
• Question #6b062
• Question #6b066
• What is the formula for frequency?
• How can I calculate wavelength of radio waves?
• How can I calculate wavelength in meters?
• How can I calculate wavelength of a photon?
• How can I calculate the wavelength from energy?
• How do you calculate the wavelength from speed?
• How do you calculate the frequency of a wave?