This character is a Other Symbol and is commonly used, that is, in no specific script.
The glyph is not a composition. Its width in East Asian texts is determined by its context. It can be displayed wide or narrow. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. U+2668 offers a line break opportunity at its position, except in some numeric contexts.
The CLDR project calls this character “hot springs” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: hot, hotsprings, springs, steaming.
This character is designated as an emoji. It will be rendered as monochrome character on conforming platforms. To enable colorful emoji display, you can combine it with Variation Selector-16: ♨️ See the Emojipedia for more details on this character’s emoji properties.
The Wikipedia has the following information about this codepoint:
In Japan, onsen (温泉) are hot springs and the bathing facilities and traditional inns around them. There are approximately 25,000 hot spring sources throughout Japan, and approximately 3,000 onsen establishments use naturally hot water from these geothermally heated springs.
Onsen may be either outdoor baths (露天風呂 or 野天風呂, roten-buro / noten-buro) or indoor baths (内湯, uchiyu). Traditionally, onsen were located outdoors, although many inns have now built indoor bathing facilities as well. Nowadays, as most households have their own baths, the number of traditional public baths has decreased, but the popularity of sightseeing hot spring towns has increased. Baths may be either publicly run by a municipality or privately, often connecting to a lodging establishment such as a hotel, ryokan, or minshuku.
The presence of an onsen is often indicated on signs and maps by the symbol ♨, the kanji 湯 (yu, meaning "hot water"), or the simpler phonetic hiragana character ゆ (yu).