If you mean ln, then lin means natural logarithm, that is, the logarithm operation based on e is the same as logarithm (see the section on logarithmic function in high school).

If you mean lim, lin means limit operation is the same as algebraic operation.

Answer over

(ln2-ln 1=ln2/ 1, that is, lna-lnb=lna/b lna+lnb=lnab)