Variable command

LAMMPS LAMMPS Beginners
1

variable Lz equal lz

Please explain what this command does?

2

Please study the documentation for the variable command — LAMMPS documentation
and get back to us with more specific questions (in case you still have any) and more information about the context of where you want to use this command and to what purpose.

Please also see 5.2. Parsing rules for input scripts — LAMMPS documentation for some background information.