I read in the internet that when an airplane stands at the airport (horizontal) it has zero degree aoa. The captain must pitch up the plane during cruise to generate an amount of lift and when the airplane pitches the relative wind also changes, and this will affect the angle of attack. This is really confusing me
You're right to be confused. The AoA can be almost anything, depending on wind direction. Normally, a wing has some camber so the lift it creates in flight is possible with an AoA of 0°. Normally, the wing is mounted at an incidence of a few degrees so the fuselage remains horizontal in flight. With this incidence and horizontal wind, the AoA at rest is just this incidence angle. But if the aircraft experiences tailwind, the AoA can be near 180°. If heated air below the wing rises up as a thermal, the AoA can be momentarily around 90°. In almost all cases, flow speed is much lower than that required for flight, but there are exceptions.
If an wing is stationary and there is no wind, then there would be no airflow and therefore no angle of attack. Assuming there was a wind, then there would be a relative airflow and so an angle at which it meets the chord of the wing.
If a stationary glider is pointing into a breeze with one wing on the ground, it is possible to lift the wing off the ground using the ailerons. This is accomplished by increasing the angle of attack of that wing, creating additional lift, despite the glider not moving forwards. Conversely, if the airflow was from behind, the ailerons would be used in reverse (opposite aileron) - a consideration for glider pilots trying to keep wings level as they slow down if they land in a tailwind.