There are five discontinuies inside the earth.

✅ Conrad Discontinuity:  Transition  zone between SIAL and SIMA.

Mohorovicic Discontinuity:  Transition zone between the Crust  and Mantle.

Repiti Discontinuity: Transition zone between Outer mantle and Inner mantle.

Gutenberg Discontinuity: Transition zone between Mantle and Core.

Lehman Discontinuity: Transition zone between Outer core and Inner core.