This character is a Control and is commonly used, that is, in no specific script. The character is also known as CANCEL.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Boundary Neutral. When changing direction it is not mirrored. U+0018 prohibits a line break before it.
The Wikipedia has the following information about this codepoint:
In telecommunication and character encoding, the term cancel character refers to a control character which may be either of:
"CAN", "Cancel", U+0018, or ^X used to indicate that the data with which it is associated are in error or are to be disregarded. Exact meaning can depend on protocol. For example:
In some journalistic text transmission formats, it signifies that the preceding word should be deleted; it is sometimes called "Kill Word" ("KW") in this context.
In some Videotex formats, it stops any running macros. In others, it clears the current line after the cursor position (compare EL).
"CCH", "Cancel Character", U+0094, or ESC T used to erase the previous character. This character was created as an unambiguous alternative to the much more common backspace character ("BS", U+0008), which has a now mostly obsolete alternative function of causing the following character to be superimposed on the preceding one.