Subscript on Orbitals
As a high school student, here’s how I considered it:

The wavefunction of an orbital describes the region of space that an electron residing in that orbital would be in about 90% of the time. 

The wavefunctions would have a radial component (depending on period), which is why the 3p orbitals Arena larger than the 2p etc.

The wavefunction would also have an angular component, which would describe its shape. 

In the case of the p orbitals, the x, y and z labels simply means that their angular components are x/r, y/r and z/r respectively (hence the subscript). Do note that we usually use the radial forms of the wavefunctions though.

Hope this helps.