When does a solar eclipse take place ? Does it occur on every new moon's day?

When the moon comes in between the sun and the earth, the moon casts its shadow on the earth and in the part of the earth which lies in the umbra of the moon, the sun is not visible. Thus, total solar eclipse occurs.

No, solar eclipse does not occur on every new moon's day because the Moon's orbit is slightly tilted with respect to Earth's orbit. Due to this tilt, the Sun, Earth, and Moon do not always line up perfectly in a straight line during every new moon's day.