A workforce is a group of people who work together to perform tasks and complete projects. Think of it like a big team of grown-ups who have different jobs to do, but they all work together to get things done.
Let's say you go to a big store, like a grocery store. You see all the people working there - the cashiers, the people who stock the shelves with food, the people who help you find what you're looking for. All of those people are part of the workforce of that store.
Sometimes a company or business will have a big workforce with lots of people working for them, and other times it will be a small workforce with just a few people.
The workforce is important because it's made up of people with different skills and abilities who can work together to make things happen. Without them, businesses and organizations wouldn't be able to function properly or accomplish the things they need to do.