First of All, I would like to say that the Earth isn't between the Sun and Moon in both of the following cases, but here's a detailed explanation :
- During a full moon, Earth is not between the Sun and the Moon. At the time of a full moon, the Sun, Earth, and Moon are aligned in that order. The side of the Moon facing Earth is fully illuminated by the Sun, which is why we see a complete, fully lit lunar disk.
- During a lunar eclipse, however, Earth is indeed between the Sun and the Moon. A lunar eclipse occurs when Earth passes directly between the Sun and the Moon, casting its shadow on the Moon. This causes the Moon to temporarily darken and take on a reddish hue due to the scattering of sunlight by Earth's atmosphere.
Though It is an answer to be done in simple words, I like explaining more.
Hope the answer works for you my friend !