Question

what is sublimation?

Answer 1

it is the direct conversion of solid state to gaseous state
like camphor is a sublime
crystal of AlCl3

Answer 2

solid carbon dioxide is another example

Answer 3

@RajshikharGupta is correct. On the Microscopic level it is the process of detachment of single molecules directly from the surface of a solid . Thsi is rare since ususally the raise in T first produces the overall "loosening" of the bonds WITHOUT single molecule detachment and this is called liquification (as opposed to sublimation)