UM3 batteries are standard AA batteries, which are produced across multiple battery types. The most common types of AA battery are alkaline, NiMH and lithium. UM3 is the JIS name for AA batteries.
JIS, or Japanese Industrial Standard, is the set of standards used by Japanese industries. These standards have been in place since 1921, and have been published in their current, simplified form since 1945. They are used in tandem with the international ISO system of standards. Some of their specifications are equivalent to ISO standards, while others specify standards for Japanese written characters and other elements that are not applicable internationally.