The evolution of advanced inverter-based resources (IBR) is closely coupled with the growth of their applications in electric power networks. Most applications of inverters during this transition were grid-following (GFL) inverters. As IBRs gradually displaced rotating synchronous generators in electric power grid applications, issues such as the behavior of low-inertia grids, local needs for voltage support, and ride-though requirements led to the first interconnection requirements. The initial DER standard, IEEE Std 1547-2003, had to be adapted to the new context and led to the revised standard, IEEE Std 1547–2018 and later the IEEE Std 2800–2022 for transmission IBR systems. In this article, the various inverter operating modes and functions of modern inverters are described. A focus on the comparison of GFL and grid-forming (GFM) inverters based on a more comprehensive white paper developed by the SCC-21 Task Force on Advanced Inverters supporting industry standards is needed in the next few years to reduce system-wide IBR events on the electric system.