What is the meaning of the word parties versus Party's and Parties?

What is the meaning of the word parties versus Party's and Parties?
partys: is not a word.party's: is to show possession, i.e. - This party's music is lame.- or -to show a contraction (to omit the letter "i" from the word 'is' and combine it with the word 'party') i.e. - This party's lame.parties: is the plural form of party, more than one party. i.e. - I went to two parties this weekend.