Meaning: This means that when people work together as a team, they are stronger and more likely to succeed than when they work alone.
Choice of Words: The word "strength" means the ability to do something difficult or to resist something. "Unity" means the state of being joined together or as one. "Weakness" means the lack of strength or power. "Division" means the state of being separated or split into parts. When you put them together, the sentence means that when people are united, they are strong, but when they are divided, they are weak.