Public opinion brigades are groups of people who work together to influence the way others think about a particular person, group or topic. It's like when you and your friends all like the same toy, and you tell other kids how cool it is, so they want to play with it too.
The people in these brigades might use social media, political rallies, or other public events to share their opinions and try to convince others to agree with them. They might use catchy slogans or persuasive arguments to get people excited about their cause.
Some people are in public opinion brigades because they believe strongly in a particular cause, while others might be paid to promote a certain point of view. Whatever the reason, these brigades can be very powerful and have the potential to shape public opinion on important issues.