Application of gauss law

Dear student,


Gauss's law is applied with two ways.

1. if we know the distribution of charge. then, we can find the electric field using this law.

2. if we know the electric field in the given region, then, we can apply the gauss's law to find the distribution of charge within this region.

examples 
to find the electric field due to point charge, charged sheet, charged plane surface etc.
to find the electric field due to solid charged sphere, shell, cylinder etc. and if we know the electric field, we can find the distribution of charge also.

with regards