This character is a Decimal Number and is commonly used, that is, in no specific script. The codepoint has the decimal value 1.
The glyph is a wide version of the glyph Digit One. Accordingly, its width in East Asian Text is fullwidth. In bidirectional text it is written as European number from left to right. When changing direction it is not mirrored. This number joins with other adjacent letters and numbers to form a word. U+FF11 offers a line break opportunity at its position, except in some numeric contexts.
The Wikipedia has the following information about this codepoint:
1 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of unit length is a line segment of length 1. In conventions of sign where zero is considered neither positive nor negative, 1 is the first and smallest positive integer. It is also sometimes considered the first of the infinite sequence of natural numbers, followed by 2, although by other definitions 1 is the second natural number, following 0.
The fundamental mathematical property of 1 is to be a multiplicative identity, meaning that any number multiplied by 1 equals the same number. Most if not all properties of 1 can be deduced from this. In advanced mathematics, a multiplicative identity is often denoted 1, even if it is not a number. 1 is by convention not considered a prime number; this was not universally accepted until the mid-20th century. Additionally, 1 is the smallest possible difference between two distinct natural numbers.
The unique mathematical properties of the number have led to its unique uses in other fields, ranging from science to sports. It commonly denotes the first, leading, or top thing in a group.