What is the meaning of -'?

Possessive marker used on plurals that end with -s (or -es, etc).

Possessive marker sometimes used on singular names which end in s, indicating than an object belongs to the noun bearing the marker.

forms the possessive of words ending in s, x or z

Genitive suffix for words that end in a sibilant consonant. For other names, -s is used.

alternative form of -a' (possessed noun suffix), used with terms ending in a vowel.

A written marker used to form the genitive of a noun phrase whose final word ends in ⟨s⟩, ⟨x⟩ or ⟨z⟩.

Source: wiktionary.org