A colander is a metal, plastic or ceramic bowl with a perforated bottom and sides. It is used straining liquids from solid foods, and a colander comes in handy when you need to rinse a number of small vegetables or fruits (like beans and grapes). Colanders are also used to strain pasta, separating it from the water it was cooked in. Some people use colanders with large holes to make spaetzle, or German-style dumplings.
To use for rinsing: Place the solid foods (such as fruits or vegetables) in the colander that you need to rinse. Then hold the colander under running water in the kitchen sink, gently shaking the colander back and forth to shift the fruits or vegetables so all sides are rinsed.
To use for straining: Set the colander in the kitchen sink and pour the food that needs to be strained (such as pasta or beans cooked in water) into the colander. Pick up the colander by the handles and gently tilt it back and forth to allow more liquid to run out; be sure to use oven mitts to avoid getting burned by the hot water. Leave the pasta or beans in the colander and rinse with running water if desired.
To make spaetzle: Pour the batter into a colander with large holes, hold the colander over a pot of boiling water, and push the batter through the holes with a spatula. When the spaetzle rises to the water's surface, scoop out the pieces with a slotted spoon.
The size of a colander's holes varies -- make sure the holes are smaller than the solid it is meant to hold.