What are unit cells? State its types. Enlist the characteristics of unit cell. Explain different types of unit cells.

(N/A) unit cell is the smallest repeating structural unit of a crystalline solid which,when repeated in three dimensions,generates the entire crystal lattice.
Characteristics of a unit cell:
$A$ unit cell is characterized by six parameters: three edge lengths $(a, b, c)$ and three interfacial angles $(\alpha, \beta, \gamma)$.
Types of unit cells:
$1$. Primitive unit cells: Constituent particles are present only at the corner positions.
$2$. Centred unit cells: Constituent particles are present at positions other than corners in addition to those at corners.
Types of centred unit cells:
$(i)$ Body-Centred Unit Cells: Contains one constituent particle at its body-centre in addition to the corners.
$(ii)$ Face-Centred Unit Cells: Contains one constituent particle at the centre of each face in addition to the corners.
$(iii)$ End-Centred Unit Cells: Contains one constituent particle at the centre of any two opposite faces in addition to the corners.