Good question! It can be confusing with all the different types of metals out there. It's an alloy combined of copper and tin. It is typically a dull yellow color that closely resembles the color of 18k gold. It will age over time if you don't clean it or protect it.
Think: Roman sculptures.
I personally love how Bronze ages over time. The patina adds a beautiful quality to it.
NOTE: Bronze can turn your skin a light black color. This is not an allergic reaction but a chemical reaction. It is due to your body's natural ph reacting to the copper. It can easily be removed by washing with warm soap and water.
TIP: You can help deter this reaction by limiting the contact with your skin. The easiest way to do this is using clear nail polish as a barrier. Put it on the inside of your ring. This is a temporary fix so it'll need to be reapplied regularly.