Why doesnt the entire earth experience the eclipse?

Not the entire Earth experiences an eclipse because the alignment required for an eclipse—where the Moon passes between the Earth and the Sun (solar eclipse) or the Earth passes between the Sun and the Moon (lunar eclipse)—only occurs in specific regions. The shadow of the Moon or the Earth only covers a portion of the Earth's surface during these events. Additionally, the curvature of the Earth means that only those in the direct path of the shadow will see the eclipse, while others may see a partial eclipse or none at all.