What is biodiversity?

If the word biodiversity is broken down into its root components we have bio, which means life, and diversity, which essentially means variety.  Putting them together gives us the variation of life forms.
  
According to Essentials of Conservation Biology by Richard B Primack biodiversity is defined as "the complete range of species, biological communities, and their ecosystem interactions and genetic variation within species (Primack 2014.)"

Reference:
Primack, R. B. (2014). Essentials of conservation biology. Sunderland, MA: Sinauer Associates, Inc.