Dorothy already linked the list of what actions earn points - they are simply meant to encourage (constructive) participation here in G2G which in turn helps to achieve Wikitree's collaborative goals.
Both questions and answers earn points - as up votes earn points "better" questions and answers earn more points. Obviously there is subjectivity in what is a 'better' answer, but generally answers that a) actually answer the question, B) refer to sources where appropriate, and c) are friendly/polite earn more votes and are more likely to be the 'best' answer. Questions that earn more votes may be a suggestion for improving Wikitree that lots of people agree with, a question many people are interested in knowing the answer to, or starting a needed discussion about disputed facts on a profile, etc., polite, comprehensible questions that show the questioner made an effort are likely to earn more points than a vague question that the questioner could have answered themselves with little effort.
