Grid-following inverters mimic current sources at their output terminals, whereas grid-forming inverters act like voltage sources and have control of voltage magnitude of frequency/phase. In contrast to inverter-based grid-following sources, inverter-based grid-forming sources would be designed to establish frequency and control voltage autonomously, and therefore they might be designed to both provide black-start capability and facilitate system restoration following a blackout. Source: https://www.nrel.gov/docs/fy21osti/73476.pdf