Beakers are the workhorse reaction vessel of the chemistry lab. They come in a variety of sizes and may vary slightly in shape but are always roughly cylindrical with a flat bottom, wide opening and pour spout.
Standard beakers are considered low-form (Griffin beakers) and are generally 1.4 times taller than they are wide. Tall form beakers (Berzelius beakers) are about twice as tall as they are wide. Flat beakers are wider than they are tall and provide significant surface to allow for faster vaporization of liquids during lab processes.
The flat bottom makes beakers stable containers for use on hot plates or placement on wire gauze for heating. The wide opening makes it easy to add chemicals for carrying out reactions and the pour spouts allows the beaker's contents to be easily poured into other containers.
Although beakers are graduated with varying levels of precision, they are not accurate tools for measuring volumes. In fact, the graduations on a typical beaker are 5-10% from the actual volume. For example, a 100mL reading of liquid in a 150mL beaker will really be anywhere between 85mL and 115mL.
Due to the presence of the pour spout, beakers are difficult to seal for chemical storage. For short periods of time a watch glass or larger inverted beaker may be placed over a beaker to reduce evaporation and the introduction of contaminants. During chemical reactions a watch glass should be used to avoid spattering of chemicals.