This character is a Other Symbol and is commonly used, that is, in no specific script.
The glyph is a square composition of the glyphs Glyph for U+006CLatin Small Letter L, Glyph for U+006DLatin Small Letter M. Its East Asian Width is wide. In bidirectional text it is written from left to right. When changing direction it is not mirrored. U+33D0 offers a line break opportunity at its position, except in some numeric contexts.
The Wikipedia has the following information about this codepoint:
The lumen (symbol: lm) is the unit of luminous flux, a measure of the perceived power of visible light emitted by a source, in the International System of Units (SI). Luminous flux differs from power (radiant flux) in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to various wavelengths, this weighting is standardized by the CIE and ISO. One lux is one lumen per square metre.
The lumen is defined in relation to the candela as
1 lm = 1 cd·sr.
A full sphere has a solid angle of 4π steradians, so a light source that uniformly radiates one candela in all directions has a total luminous flux of