Anisotropy and Isotropy is a behavioural characteristic which can be used to differentiate between the two types of solids that are, crystalline and amorphous solids.
It is specifically shown by crystalline solids . So, basically, if I say that crystalline solids are anisotropic in nature it means that this type of solid will show different values of a physical property among different directions. For eg, Quartz is a crystalline solid and it shows different values of refractive index amongst different directions.
It is specifically shown by amorphous solids . So, basically, if I say an amorphous solid is isotropic in nature it basically means that this type of solid will show same values of a physical property amongst different directions. For eg, Quartz Glass is an amorphous solid and it shows the same value of refractive index among different directions.
NOTE : In this answer I have specifically taken refractive index as the physical property to explain the terms precisely. You can take any other physical property too.