What is Coulomb’s law of electrostatics?

What is Coulomb’s law of electrostatics? 

First Law: 

Like charges of electricity repel each
other and unlike charges attract each
other.

Second law:

The force (F) exists between two
point-source charges (Q1 and Q2) is
directly
proportional to the product of the
two charges and is inversely
proportional to the square of the
distance (d) between the charges.

1.10 Capacitance:

The amount of charge that a capacitor
can store per unit of voltage across its
plates is
its capacitance. It is represented by C.
The capacitance is a measure of a
capacitor’s ability to store charge.
Farad is the unit of capacitance.
One farad is the amount of
capacitance when one coulomb of
charge is stored with
one volt across the plates.
F α Q1 Q2
d2
F = k.Q1 Q2d2 Constant,      k = 14πεoε
r
   Where, F = Force between the
charges (N)
Q1 and Q2 = Magnitude of two charges
in coulomb
F = Force between the charges (N) d =
distance between the charges (m) εo  =
Permittivity of the free space
In S.I:        εo  = 8.854x 10−12 farad/
metre
εr = relative permittivity of the medium
εr = 1 for vacuum or air
   Therefore,    Force:     F = Q1 Q24πεoε
rd2
F = Q1 Q24π x 8.854x 10−12  x εrd2 F =
9 x 109x Q1 Q2
εrd2         ; for a medium
F = 9 x 109x Q1 Q2d2         ; for air