Hi Praveen :

Primary Succession can be defined as the process of growth in an area that was previously uninhabited, barren, unoccupied and there was no initial vegetation. On the other hand,

Secondary Succession can be defined as the growth of the community in such area which was previously occupied, inhabited and that has primary vegetation but got disturbed or damaged due to some external or internal factors.

The example of Primary Succession is the newly formed bare rock, desert, ponds, etc.

The area covered under deforestation, or affected by natural calamities such as flood, earthquake, etc. are the examples of Secondary Succession .

Hope this was helpful!