In the 8086 architecture, which is the architecture that DOS targeted, memory references are composed of two parts: a 2-byte segment “identifier” and a 2-byte offset within the segment.

Memory addressing in which each byte is referenced by a base number (the segment) plus an offset. An x86-based PC running in 16-bit mode (Real Mode and Virtual 8086 Mode) uses 64KB segments ...

When the 8086 processor recovers from a hardware ... has to be a far jump to somewhere higher up in memory, and load the Code Segment and Instruction Pointer to the place where your program ...