Space Lattice:

A Space lattice is defined as an array of points arranged in a regular periodic fashion in three dimension such that each points in the lattice has exactly identical surrounding. It is a skeleton upon which crystal structure is built by placing atoms on or near the lattice points.

Unit Cell: 

The Unit Cell is a smallest geometric figure, the repetition of which in 3-dimention gives the actual crystal structure. It is also called as a primitive cell. It is the fundamental elementary pattern (structure of solid) of minimum no. of atoms/molecules/ groups of atoms which represent all the characteristics of crystals

Lattice parameter:

Three Primitive Vectors: a, b and c length of the three edges of the unit cell and represent the crystallographic axes

Three inter-axial Angles: a, b and g

a: Angle between the edges b and c

b: Angle between the edges a and c

g: Angle between the edges a and b

The axial length a, b, c and the three inter-axial angles a, b and g are called Lattice Parameter