Indirect rule is when a powerful group or person rules over another group or people through someone who belongs to that group or people. Think of a parent having a babysitter watch their child. The parent is the one in charge, but they might use the babysitter to help make sure their child behaves well and follows the rules.
In history, some countries used indirect rule to control people they had conquered or colonized. They would choose someone from that group or people who was willing to work with them and put them in charge, but the person in charge would still follow the rules set by the conquerors. For example, during British colonization in Africa, local rulers were often allowed to stay in power but they had to follow British rules and policies.
This could be good for the conquerors because it made it easier to control the people since they had someone who spoke their language and understood their culture making the rules. However, it was also bad for the people being ruled over because they often had little say in their own governance and could be mistreated by the person in charge who may have been more loyal to the conquerors than to their own people.