This character is a Other Symbol and is commonly used, that is, in no specific script. The character is also known as level control.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. U+1F39A offers a line break opportunity at its position, except in some numeric contexts.
The CLDR project calls this character “level slider” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: level, music, slider.
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:
A slider or track bar is a graphical control element with which a user may set a value by moving an indicator, usually horizontally. In some cases user may also click on a point on the slider to change the setting. It is different from a scrollbar in that it is not continuous but used to adjust a value without changing the format of the display or the other information on the screen.
Its most popular use is for viewing and jumping to a playback position in media player software.