The goal of investing is to have your money work for you. The main idea is to take a sum of money, the capital, and put it somewhere, either in a company or a project, or some other place which it is believed will grow in value. If growth actually takes place, then the share of the business or project which you purchased should be worth more money than it did when you invested in it, and if you sell your share, you will make a profit. That is the nuts and bolts of investing.
The project or business in which the money is invested is called the instrument, through which money increases, hopefully, in value. Almost all investment instruments are associated with risk. Usually the higher the risk an investor is willing to take, and then the potential rewards are commensurate with those higher risks. Investors need to always be aware that there is no such thing as a sure thing, and that even investments that seem risk-free can lose money.