Basis points are used as a convenient unit of measurement in contexts where percentage differences of less than 1% are discussed.
It is common practice in the financial industry to use basis points to denote a rate change in a financial instrument, or the difference (spread) between two interest rates, including the yields of fixed-income securities.
Expense ratios of investment funds are often quoted in basis points.
The same unit is also (rarely) called a permyriad, literally meaning "for (every) myriad (ten thousand)".
(It can be regarded as a stylized form of the four zeros in the denominator of "1/10,000", although it originates as a natural extension of the percent % and permille ‰ signs).