Flower bud
Sepals are attached to the top of the stem of the flower. After the flower is completed formed the sepals open. This allows the petals to open and spread to expose the inside of the flower. Sepals in some plants are thorny or hairy to protect the plant and in some fall off after the flower opens.
Sepals protect the tender flower parts in the flower bud and being green in color perform photosynthesis also.
A flower has petals, sepals, pistols and stamens.
The sepals protect the tender parts of the flower in the unopened flower.
The sepals of a rose flower are the green leaf or petal like structures (usually 5) that are used mainly to protect the flower bud before it blooms. After the flower blooms I suppose flower no longer needs it's sepals, and the plant can certainly survive without sepals, if you really wanted to remove them.
Sepals protect a young flower by enclosing it before it blooms. Sepals are usually green and located at the base of the flower.
Morphologically both sepals and petals are a modified leaf. When the flower is in bud, the typical function of the sepals is to enclose and protect the more delicate floral parts within. The sepal also helps protect the delicate petals from bug attacks. Sepals in most flowers are green and lie under (or around) the more conspicuous petals. The rose is one example of a flower with a sepal.
receptacle
A flare Sepals of a flower are collectively called 'calyx'
Some sepals are green but not all are green. It is a modified leaf that protects the flower bud. But sometimes the sepals have as much color as the petals. In daylilies, there are three petals and three sepals. The sepals may have the same color and pattern as the petals or different.
it protects the flower from anyone trying to hurt it
Each of the parts of the calyx of a flower, enclosing the petals and typically green and leaf like.