Social mobilisation means getting lots of people to work together on a problem or a goal. It's like a big team effort to achieve something.
Let's say you and your friends want to clean up the neighborhood park. You could all work on your own, picking up a few pieces of trash here and there. But it would take forever and not much progress would be made. Social mobilisation means getting all your friends to work together to clean up the whole park at once. You could divide the work, like some people picking up trash, some people raking leaves, and some people sweeping. And together, you can achieve the goal of a clean park much faster.
Social mobilisation can happen for all kinds of things, like raising money for a charity, organizing a protest against something unfair, or building a community garden. It's all about getting lots of people to work together to make a difference. And when we work together, we can do amazing things!