The act of putting money in any instrument such as stocks, bonds, FDs etc with the intention of increasing the value of your money or making a profit is called an investment.
It is usually a time-taking process meaning that profits in most cases are not immediate and risks vary according to the product you invest in.

Example:
If you have some extra money and decide to put it aside to earn interest on it by putting it in a fixed deposit, mutual funds or a government scheme, it is called an investment. The risk may be lowest in FDs