For applications, Members vote for applicants whether they think they'd be suitable as an admin and member of the F|A clan using +1 for a positive vote and -1 for a negative vote. The more +1 votes you get the better. If you get a -1 vote. Don't worry, work on the criticism they provide and turn that -1 into a +1. End of the day, we wan't more people to join our community to keep it fun and fair.
You will most likely only see +1/-1 in applications. The reaction system is used for everything else.