Most French adjectives go after the noun they describe, the opposite of English: une voiture rouge (a red car), un livre intéressant (an interesting book). This is the default position and applies to the vast majority of descriptive adjectives, especially those describing color, shape, nationality, and religion.
A small, frequently used set of short adjectives instead comes before the noun — often remembered with the acronym BAGS (Beauty, Age, Goodness, Size): beau, joli, vieux, jeune, nouveau, bon, mauvais, grand, petit, gros. So it's un grand homme (a tall/great man) but un homme intelligent (an intelligent man).