Mr. Jones votes for a party. There are several party's in Germany, not only Democrats and Republicans. So Mr. Jones votes for one of them. A party gets members in the Bundestag, if they get more than 5% of the votes. If a party has less than 5% of the votes, are they not allowed to participate in the Bundestag.
You can not only vote on a party, but also on a person of a specific party. If a party will have 10 representatives, the first 10 on the vote list will participate in the Bundestag. But if you're the 11th on the list, you can still join your party in the Bundestag if you get enough, so called 'preference votes' on you as person.
So a party can send a limited number of members to the Bundestag, but Mr. Jones can influence which members. Members at the same party will usually vote the same in the Bundestag, but, like Democrats and Republicans, they can also vote else.
Note: the votes at party's who didn't get enough votes to participate in the Bundestag, will be divide. So if party A has 30% of the votes, they get some extra votes from the party's who didn't passed 5%. Party A will have 32% of the members in the Bundestag then.
(Not sure if this is the complete system, I'm from Holland)