High-temperature superconductivity in iron-based materials has been a major focus of research since its discovery in 2008. The discovery of superconductivity in fluorine-doped LaFeAsO at 26 K marked the beginning of extensive studies on this family of materials. Over the past two years, numerous publications have emerged, highlighting the unconventional nature of the Cooper pairing state in these systems. Key questions remain, including the role of magnetism, the nature of chemical and structural tuning, and the pairing symmetry. The search for universal properties and principles continues. Iron-based superconductors (FeSCs) are distinct from cuprate superconductors, with similar interplay of magnetism and superconductivity. The phase diagram of FeSCs is strikingly similar to other unconventional superconductors, including cuprates, organics, and heavy-fermion systems. The interaction leading to high-temperature superconductivity is believed to originate within the common iron layers, similar to the copper-oxide building block in cuprates. Chemical substitution plays a key role in inducing superconductivity in iron-pnictides, but three key differences exist compared to cuprates: (1) the arrangement of pnictogen/chalcogen anions above and below the planar iron layer; (2) the ability to substitute or dope directly into the active pairing layer; and (3) the metallic nature of the parent compounds. The generic phase diagram of FeSC systems can be manipulated through chemical or structural properties, using either chemical doping/substitution or applied external pressure to drive an antiferromagnetic (AFM) parent compound to a superconducting (SC) state. The phase diagram of the Ba-based "122" system is the most widely studied, with systematic substitution of elements producing a phase diagram with an AFM state that is suppressed with substitution and a SC phase centered near the critical concentration where AFM order is destroyed. This is somewhat different from the behavior of F-doped "1111" systems, where AFM and SC phases are completely separated. Pressure tuning is less well understood, with some cases showing alignment with chemical substitution. However, in pressure experiments on BaFe2As2, differing experimental conditions impose variations from true hydrostatic conditions, making it difficult to generically compare phase diagrams. The sensitivity of the superconducting phase to particular choice of ion substituent is highlighted by the fact that superconductivity in 122 materials can be stabilized by several types of d-metal substitution, including elements in the Fe, Co, and Ni columns, but excludes Cr, Mn, and Cu, which suppress magnetism without stabilizing a SC phase. The electronic structure of FeSCs is complex, with magnetic and electronic interactions playing an integral role in determining the phase diagram. These materials are well described as consisting of two-dimensional (2D) metallic sheets derived from Fe d-states hybridized with AsHigh-temperature superconductivity in iron-based materials has been a major focus of research since its discovery in 2008. The discovery of superconductivity in fluorine-doped LaFeAsO at 26 K marked the beginning of extensive studies on this family of materials. Over the past two years, numerous publications have emerged, highlighting the unconventional nature of the Cooper pairing state in these systems. Key questions remain, including the role of magnetism, the nature of chemical and structural tuning, and the pairing symmetry. The search for universal properties and principles continues. Iron-based superconductors (FeSCs) are distinct from cuprate superconductors, with similar interplay of magnetism and superconductivity. The phase diagram of FeSCs is strikingly similar to other unconventional superconductors, including cuprates, organics, and heavy-fermion systems. The interaction leading to high-temperature superconductivity is believed to originate within the common iron layers, similar to the copper-oxide building block in cuprates. Chemical substitution plays a key role in inducing superconductivity in iron-pnictides, but three key differences exist compared to cuprates: (1) the arrangement of pnictogen/chalcogen anions above and below the planar iron layer; (2) the ability to substitute or dope directly into the active pairing layer; and (3) the metallic nature of the parent compounds. The generic phase diagram of FeSC systems can be manipulated through chemical or structural properties, using either chemical doping/substitution or applied external pressure to drive an antiferromagnetic (AFM) parent compound to a superconducting (SC) state. The phase diagram of the Ba-based "122" system is the most widely studied, with systematic substitution of elements producing a phase diagram with an AFM state that is suppressed with substitution and a SC phase centered near the critical concentration where AFM order is destroyed. This is somewhat different from the behavior of F-doped "1111" systems, where AFM and SC phases are completely separated. Pressure tuning is less well understood, with some cases showing alignment with chemical substitution. However, in pressure experiments on BaFe2As2, differing experimental conditions impose variations from true hydrostatic conditions, making it difficult to generically compare phase diagrams. The sensitivity of the superconducting phase to particular choice of ion substituent is highlighted by the fact that superconductivity in 122 materials can be stabilized by several types of d-metal substitution, including elements in the Fe, Co, and Ni columns, but excludes Cr, Mn, and Cu, which suppress magnetism without stabilizing a SC phase. The electronic structure of FeSCs is complex, with magnetic and electronic interactions playing an integral role in determining the phase diagram. These materials are well described as consisting of two-dimensional (2D) metallic sheets derived from Fe d-states hybridized with As