Crème is the French word for cream, the high-fat portion of milk skimmed or separated out before further processing. On its own, "crème" is a generic term rather than one specific product - it appears in dozens of named preparations, from crème fraîche (cultured, tangy) and crème anglaise (a stirred custard sauce) to crème brûlée and crème caramel (baked custards), each meaning something different despite sharing the word.
As an ingredient, cream thickens and enriches: it's the base of béchamel-style sauces, the finishing touch in many pan sauces and soups, and the structural fat in custards, mousses, and ice creams. In French cooking it's foundational to béchamel sauce, crème fraîche, and crème brûlée; the same dairy fat underlies carbonara and tiramisu in Italian cooking. Southeast Asian curries and sauces often use coconut cream instead, which plays a similar role but is a plant-based cream, not dairy crème.
Cream pairs well with fruit, chocolate, nuts, and warm spices, since its fat can round out acidity, bitterness, and heat.