For thousands of years gold has been used as money. Before paper money and bank-backed currency gold was always known as money. Even today gold holds it’s value very well and is known as one of the safest investments a person can use in order to hold value.
Gold bars are a common form of gold bullion. Gold bars tend to be purchased by serious investors and not collectors. Gold bars can hold a high weight of gold which obviously increases it’s general value.
Gold coins are the most common form of traded gold. Not only do they have value in their gold weight, but some gold coins can have increased value because of collector value. The year the coin came out and which design it has on it can play into this equation. Gold coins usually cost less than gold bars.