Port-Royal Logic is a way of finding the truth or falsehood of things we say or think. Imagine you have a toy box with different toys, and you want to know if a toy is inside or not. Port-Royal Logic helps you do this by looking at the different parts of the toy box - the bottom, the sides, and the top.
Now, let's say you have a sentence like "The sky is blue." Port-Royal Logic helps you see if this sentence is true or false by looking at different parts of it. It checks the "bottom" part, which is the meaning of the words - is "sky" referring to the actual sky and is "blue" the correct color for it? It also looks at the "sides" part, which asks if the sentence contradicts other things we know to be true or false. For example, we know the sky can be gray on a rainy day, so that may contradict our sentence. Lastly, it looks at the "top" part, which is the context or situation in which the sentence is said. If someone is colorblind and says "the sky is blue," they may be mistaken even if it is generally true.
By looking at these different parts with Port-Royal Logic, we can understand if a sentence is true or false, and this helps us make better decisions based on facts rather than assumptions.