sigma and pi bonds in p orbital

[Courtney_Koenig_3K]

In the p orbitals, px and py are pi bonds and pz is sigma bonds. Why are there two pi bonds and one sigma bond, and why is it the pz orbital that has the only sigma bond?

[JennaMinami1I]

Hello!

Pi bonds occur due to side by side overlapping of atomic orbitals in a plane
Sigma bonds occur due to end to end overlapping of atomic orbitals

Overlapping p orbitals can either form pi or sigma bonds. The way the bond orients and overlaps depends which one it is.
Here is a picture that I found helpful for visualization of this concept