Majority rule is a way of making decisions in government or in voting. A decision is made if it gets more than half of the votes. Majority rule is often used in referendums, which is when voters decide if they want to make a law by voting yes or no.
Majority rule is not the same as a plurality vote. In Plurality voting, which is often used in elections, whoever gets the most votes wins. With a plurality vote, the winner can have fewer than half of the votes if there are more than two choices.
Some people have criticized majority rule because it can lead to the tyranny of the majority which is not true democracy, where people who are the majority might vote for something that helps them but hurts the people in the minority.