There was a time when people were taught that there are only three states of matter available, namely solid, liquid, and gas. Over the past years, the machines and tools that researchers and scientists use have become more advanced. They are able to identify some differences with the available states of matter.
The five states of matter now are solid, liquid, gas, plasma, and the last one is man-made and called Bose-Einstein Condensates. Plasma is a state that is not very common here on earth, but it can be the most prevalent for the rest of the universe.
This is composed of highly charged particles that are obviously different from gas. These two are often compared because of some similarities. BEC, on the other hand, was just created in 1995. If you learned about the three states of the matter before 1995, then this is highly understandable.