The best way to explain it is to make a good statement rather than making a long and very technical definition that is hard for the reader to understand. So here is my explanation " All trading is an investment but not all investment is trading". It simply means that even trading itself is considered as investment. But investment has many forms aside from just trading, it could be investment in networking, loans, business and many more.
You are absolutely correct! What a very concise and precise answer. Trading is buy and sell. It is one of the many types of investments. And it is the most common type. It is already part of the lives of our ancestors. Hence, this type of investment is very old, older than all of us here.