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.
That is even harder for a newbie to understand!
OP when you are trading, you are actually investing your money(or coins) as well.
In the real world people see investment as when you buy something and wait for the price to rise before selling - the same thing applies to those who hold bitcoins for a long time, they are waiting for the price to rise.
Now we have the day-traders who buy a coin and sell within a few days, they make "small" profits daily or weekly because the price of all coins changes everyday - if you check any exchange you will see the 24hour-high and 24hour-low prices.
This is how day-traders operate.