What is the difference between a galaxy and a nebula?

A galaxy is a massive, gravitationally bound system containing billions of stars, along with gas, dust, and dark matter. Our own Milky Way is a galaxy. A nebula, on the other hand, is a cloud of gas and dust within a galaxy. Nebulae are often the birthplaces of stars, where gravity causes material to collapse and ignite nuclear fusion, though some nebulae are remnants of dying stars, like supernova remnants or planetary nebulae. Historically the distinction was blurry because early astronomers called any fuzzy object in the sky a nebula, including what we now know are distant galaxies. Today the terms are clearly separate, with galaxies being enormous stellar systems and nebulae being interstellar clouds of gas and dust.