direct and reciprocal lattice

i have just started studying "physics of semiconductor".i have came across ,primitive cell,some cubic structures and milller indices .so far i am okay with all concept,but suddenly a concept called direct lattice and reciprocal lattice is introduced.i do not know what that mean all i have in my hand is just equation of that.

direct lattice
R=ma+nb+pc

reciprocal lattice

a*=2pi((b*c)/a.b*C)


b*=2pi((c*a)/a.b*C)


c*=2pi((a*b)/a.b*C)

please explain me about this by considering i am new to semiconductor physics.Thank you in advance