Vermiculite added to the garden or vermiculite in potting soil increases water and nutrient retention and aerates the soil, resulting in healthier, more robust plants. Perlite may also be found in potting soils, but vermiculite is far superior for water retention. Vermiculite, although less aerating than perlite, is the amendment of choice for water-loving plants.

Read more at Gardening Know How: What Is Vermiculite: Tips On Using Vermiculite Growing Medium

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/vermiculite-growing-medium.htm