In exchange for your business, If you make your very first deposit at a sports book, they will usually offer you a bigger cash bonus, compared to a reload (any deposits after your initial), which are usually much smaller.
These bonuses are more cash money added to your total, and the amounts/percentages vary.
Example: Sports Book offers a 50% cash bonus for any new player's deposit, with a 20x Rollover.
I deposit $100.
I then have an additional $50 (50%) added for a total balance of $150.
But there's a catch.
If you win, and want to cash out your money, you must first meet the rollover that is mentioned above.
These rollovers will vary with different books as well as different bonus amounts.
In this example, the rollover is 20x.
This means that I must wager my total new balance after the bonus I received, which is $150, 20 times the amount, which would equate to $3,000.
Once I have made enough wagers to teach or surpass that amount, I am free to withdraw some or all of my balance.
As mentioned, rollover amounts will vary, and some may be considered too high for a player, and they must make that decision by accepting, declining, or searching for a better deal.
Always remember, you can decline any bonus offered from a book if you do not want to to be concerned with meeting a rollover before being able to withdraw your cash.
Free Plays explanation coming from myself or someone else who chimes in.
Free plays is what a book gives you as a bonus when making a deposit or sometimes as a courtesy for making a lot of wagers with them.
Once in a while you might also get free plays from contests offered to players.
With a free play, you simply use it risk-free to make a wager, and if you win, you get the money added to your account.
Each book or site has different rules for free plays on whether they win, lose, or push, so be sure to know that ahead of time.