What is the meaning of ſ?

The long s, a form of the letter ess (S).

The nineteenth letter of the English alphabet, called long s, medial s, or descending s and written in the Latin script.

The long s, a form of the (lowercase) letter s.

A letter formerly used to represent the sound /z/, now replaced by z, and in the trigraph ſch, corresponding to modern ś; used primarily in texts written in Fraktur.

typographical variant of s, typically used for all instances except a final -s

An alternative form of s

Source: wiktionary.org