In this section will explain how odds and lines work. In most sites you will see 3 different types of odds format; decimal, fractional and American.  Most of the betting sites have the 3 formats to make the bet easier for the player but is not a bad idea to understand each format.

Decimal format:  This format is very rarely used within the United States but you will see that is very common for European, Canadian and Australian players.  For USA players can be a little confusing due to the custom of using the other formats.
I will give a few examples. Suppose that your give a 5.00 odd that means that with one dollar you're going to be paid 5. The decimal odds show how much you will be paid and fractional and the American shows how much you will go to win. If you want to change the decimal format to a fractional one you have to subtract 1 to the 5.00 and the rest turn it to fraction. For example:
Decimal(x)  to Fraction   = x-1 , then convert to fraction
5.00 -1=4.00  to fraction 4/1 

That means that you will win $4 for each $1. Like you see in the fractional format you will 4 and in the decimal you will receive 5 because they counting 1 that you bet. If you want to change from decimal to American odd, you have to use this formula:
Decimal(x) to American  =100*(x-1) if x>=2; -100/(x-1) if x<2

The difficult part to understand from decimal odds is when the odd is the favorite or minus 2. For example if an odd of 1.25 is given. That means that you will win .25 for 1. In fractional it would be ¼ that means that you have to bet 4 to win 1 that's a .25 for each 1.

Fractional format: This format is very popular in the UK and is used in horse racing odds.  It's very simple to use. Just see it in this form x/y; x is the money that you will win and y is the money you have to bet to win the x amount. Let's see some examples:
5/1: win 5 with a 1 bet
1/3: win 1 with a 3 bet

American format: This format is the most popular in the USA and is also very simple. The favorite odd will have a – and the underdog a +. For example a +350 means that with a bet of 100 you will win 350 and a -280 means that you have to bet 280 to win 100. This format is always based on 100.