Odds for different outcomes in single bet are presented either in European format (decimal odds), UK format (fractional odds), or American format (moneyline odds). European format (decimal odds) are favored in continental Europe, Canada, and Australia. They are the ratio of the full payout to the stake, in a decimal format. Decimal odds of 2.00 are an even bet. UK format (fractional odds) are favored by British bookmakers. They are the ratio of the amount won to the stake. Fractional odds of 1/1 are an even bet. US format odds are favored in the United States. They are the amount won on a 100 stake when positive and the stake needed to win 100 when negative. US odds of 100 are an even bet.
For example, if we get decimal odds (the kind I use on this blog) of 1.5, and we bet $10, we can expect to win $15. In UK odds, that would be 1/2; the moneyline would be -200.
Laying is different, and I won't be posting lays on this blog. If you are interested, you can read more at Betfair.