ELI5: Explain Like I'm 5

There's a sucker born every minute

This phrase means that some people are very easily fooled, or tricked, and that there are a lot of those people. This means that there are always people who will believe things that are untrue, or who are taken advantage of. For example, if someone says they have a magic wand that can make you rich, there might be some people who believe it and give the person money.