Pls explain the arrangement of electrons in various shells, sub shells and orbitals?

Electrons move in regions of space surrounding the nucleus called orbitals. These orbitals can be regarded as being arranged in shells around the nucleus. These shells are major energy levels surrounding the nucleus. Shells are further divided into energy levels of similar energy called subshells. These subshells are given the labels of "s", "p", "d", "f" and "g".Subshells are further composed of orbitals, which, as discussed above, are regions of space around the nucleus in which electrons can be found. The subshells within a shell increase in energy in the following order, sOrbitals can have 0, 1 or 2 electrons in them. This is known as thePauli exclusion principle.

A many electron atom fills its lowest energy shells first before proceeding to higher energy shells. The order of filling is 
1s, 2s, 2p, 3s, 3p, 4s, 3d .