This tutorial will focus on the physics of antiferroelectric materials. We’ll start by considering the definition of antiferroelectricity in analogy to the definition of ferroelectricity. We will develop a theoretical framework for describing the crystal structures and energy landscape in terms of lattice modes of a high-symmetry reference structure, using space group formalism, Landau expansions, and first-principles calculations of phonon dispersion and total energies. We will learn about electric field switching of antiferroelectrics, which will directly lead into an overview of their functional properties, including piezoelectric, electro-optic and electrocaloric effects associated with switching between the antipolar and polar states, and the resulting technological applications. Throughout, we will illustrate and reinforce the essential concepts by looking at prototypical antiferroelectric materials, including PbZrO₃, AgNbO₃, Sm:BiFeO₃ and thin-film ZrO₂, reviewing first-principles studies and experimental synthesis and characterization. We will discuss the design and discovery of new antiferroelectric materials using crystallographic databases, high-throughput first-principles calculations, and data mining.   Finally, we will consider the place of antiferroelectrics in the broader context of functional electric-field-switchable polar materials.