Hi Roshni,

Bond order simply tell us about the number of bonding pairs of electron between two atom.

Example - 

Let A and B are two atoms 

 if they forms a molecule like A - B, bond order will be One (1)

 if they forms a molecule like A = B, bond order will be Two (2)

We can use this formula to determine the bond order between atoms

Bond order = 1/2(N_b-N_a)

Thanks for asking 

Good day :)