It’s a method or scheme for performing a mental act which does not have any utility.

If it is a scientific theory or mathematical method

If it represents an aesthetic creation, literary, dramatic, artistic work, or a computer program

If it is a mere discovery and does not have an inventive step

If it is frivolous, obvious, contrary to law, injurious to public health and inventions related to atomic energy.

A method of agriculture or horticulture