For example, Pinot Noir and Gamay have inherently low-levels of tannin, whereas Nebbiolo and Cabernet have very high levels.
Tannin comes from 2 places: the skins and seeds of grapes or from oak aging. Every grape variety has a different inherent level of tannin, depending on its individual character. For example, Pinot Noir and Gamay have inherently low-levels of tannin, whereas Nebbiolo and Cabernet have very high levels.