What is a spotters guide?

A spotter's guide, field guide or handbook, is a book designed to help the user identify animals, plants, or artifacts in the field, rather than in the laboratory, herbarium, or museum. While a field guide covers a few common species, species important for conservation, or perhaps all species in a local geographic region, a handbook usually treats all known species of a taxonomic group. Spotter's guide is most commonly the title for aircraft guides, whereas field guide is more common for animal and plant identification guides.