Inflorescence derives from the Latin verb inflorescere, meaning "to begin to bloom," and ultimately from florēre, "to blossom" or "to flourish." Generally, it refers to the arrangement of flowers on the stem or stalk of a plant. Here's a bouquet of some of the more common inflorescences.
A raceme's flowers develop on short stalks of about equal length at equal distances along an unbranched, elongated axis, as exhibited in the lily of the valley. This inflorescence might recall a bunch of grapes, and, actually, its name is from Latin racemus, meaning just that, "a bunch of grapes."
The flower cluster of an umbel grows from a common center and forms either a flat or curved surface. It resembles the ribbed structure of an upside-down or right-side-up umbrella, which can be seen in the milkweed or Queen Anne's lace.
Although the flower stalks of a corymb grow at different levels along a main stem, they still reach about the same height, like that of an umbel's. The inflorescence of the yarrow grows in this manner.
The common sunflower's inflorescence is called a capitulum, which in Latin means "small head." Essentially, one can consider this inflorescence to be a bunch of small flowers embedded in a flat receptacle.