Button cell batteries take their name from their shape. They’re a popular battery for many small devices as button batteries are temperature resistant, provide a continuous voltage and have a long shelf life.
All button batteries have a unique model number which can be used to identify the correct replacement. Sometimes this code may start with letters specific to a manufacturer, for example Duracell label their CR2025 as DL2025. Luckily the four digits are always consistent and provide the size of the battery. The first two digits are the diameter and the last two are the height, so a CR2032 has a 20mm diameter and sits 3.2mm tall.