What are the properties of photons and electrons? What the hell do they have to do with each other?

Now let's talk about the photoelectric effect.

Any object that absorbs light gains energy, and some of that energy is absorbed by electrons. After absorbing energy, the electron will jump to a higher energy, but unless the electron absorbs enough energy to get rid of the nucleus, the electron will still release a photon to return to its original orbit (ground state), because the electron always prefers a more stable state, that is, the ground state. If the electrons in the outermost shell gain enough energy, the electrons are freed from the nucleus and become free electrons.

For a macro example, a stone in a valley is equivalent to a ground state (stable state), the stone always tends to be in the valley, if there is an external energy to move the stone to the hill or the top of the mountain (for example, you move the stone to the hill or the top of the mountain), the stone will always roll down into the valley and return to its original position (ground state).

Therefore, the photoelectric effect does not mean that a photon can be converted into an electron, but that when an electron absorbs a photon of a certain energy, it becomes a free electron and can generate an electric current.

In layman's terms, photons are actually produced by the motion of matter (which is basically photons), and electrons release or absorb energy (photons) in the process of transition. In the process of releasing or absorbing photons, the mass of matter will also change, which is also a reflection of Einstein's mass-energy equation, mass and energy are the same thing, and energy is something more essential.

Finally, electrons can indeed "become" photons, in two ways. The first is decay, but the process of electron decay is extremely long, scientists have calculated that the electron signature can reach 6.6×10²⁸ years. Second, it collides with positrons to annihilate them, which often happens during nuclear fusion in the core of a star!