Recent advancements in microfabrication technologies and the development of powerful simulation tools have led to a significant expansion of diffractive optics and diffractive optical components. Instrument developers can choose from a broad range of diffractive optics elements to complement refractive and reflective components in achieving a desired control of the optical field. This Field Guide provides the operational principles and established terminology of diffractive optics as well as a comprehensive overview of the main types of diffractive optics components. An emphasis is placed on the qualitative explanation of the diffraction phenomenon by the use of field distributions and graphs, providing the basis for understanding the fundamental relations and important trends. Contents: Diffraction Fundamentals Fresnel Diffraction • Fraunhofer Diffraction • Apodized Apertures • Diffraction by Multiple Apertures • Resolution Limit in Optical Instruments • Diffractive Components • Grating Properties • Blazing Condition • Scalar Diffraction Theory of Grating • Extended Scalar Diffraction Theory • Gratings with Subwavelength Structures • Rigorous Analysis of Transmission Gratings • Polychromatic Diffraction Efficiency • Efficiency of Spaced Grating Doublets • Diffractive Components with Axial Symmetry • Diffractive Surfaces in Optical Systems • Appendix: Diffractive Raytrace"