Inserts a word of data into the program with value defined by the input. In this case, a "word" is 2 bytes.
.dw n ;n is any 2-byte integer .word n
The second easiest way to put data directly into your program. Note that since the z80 processor is little-endian, loading into a 16-bit register from 2 bytes inserted using .DB will cause the least-significant-byte and most-significant-byte to be swapped.