There are some people who may become confused with these two since they may have different meanings. For meanings that mean that they are interrelated and connected to each other. These are fundamental operations that are used so that sets can be combined.
The union will make sure that the different elements in the set are in both sets or are all available in just one set. When you say intersection, this means that the different elements that can be found all belong to the different sets that you can find. Take note that the operations that will be used can also differ.