When you say an engagement ring, this is the type of ring that is given to you when you are asked for your hand in marriage. This means that you will get married in the future. Engagement rings are normally expensive especially if they are made with precious metals and stones. Wedding rings are normally given and worn on the actual day of your wedding.
The wedding ring will symbolize that you should have undying love and loyalty to each other because you are already married. There are a lot of people right now who get both engagement and wedding rings. In the past, some people never bothered to undergo the engagement because they just proceed to get married.