Around each new moon and full moon, the sun, Earth, and moon arrange themselves more or less along a line in space. Then the pull on the tides increases, because the gravity of the sun reinforces the moon’s gravity. In fact, the height of the average solar tide is about 50% the average lunar tide. Thus, at new moon or full moon, the tide’s range is at its maximum. This is the spring tide: the highest (and lowest) tide. Spring tides are not named for the season. This is spring in the sense of jump, burst forth, rise. So spring tides bring the most extreme high and low tides every month, and they happen around full and new moon. So spring tide occurs. Hope it cleared your doubt.