“Surrogate pairs” refers to the pair of 16-bit values that Unicode uses to represent any character that may require more than 16 bits.
Most characters are represented within the range [0x20, 0xFFFF], and can be represented with a single 16-bit value. A surrogate pair is a pair of 16 bit values that represent a character in the range [0x010000..0x10FFFF]. See “Example 7” for more details.
