Investing is the act of providing capital into some venture, with the expectation of receiving a return on that money.
Investing carries a risk, in some form. Even for an investment that promosies a guarantee, your risk might be in the fact that it is long-term. Meaning, that money is not tied up over years or decades, instead of coming back to soon.
Stocks and commodities are the most general investments. Others like property, businesses, bonds, government notes and currencies can also be made.
You will likely need to paid taxes on any gains made during an investment, minus your losses.