While the terms "bail" and "bond" are often used interchangably, they are in fact quite different.
Bail in the amount that the court demands you pay to secure your release. So, for instance, if the court sets you bail at $10,000 you have to pay the court $10,000 in order to get out of jail until your trial.
If you do not show up for your hearing the money is forfeited and a warrant is put out for your arrest. If you do everything you are supposed to and show up for your hearing, the money is refunded.
If you have enough money to pay your bail (and plenty of wealthy people seem to commit crimes these days) this is a pretty good deal for you since you get your money back. Most people, however, don't have this kind of money (and bail can be set at $100,000 or even $1M or more if you are considered a flight risk).
Bond (also known as a "Bail Bond")
So what do you do if the court sets your bail at $10,000 and you don't have the cash? Bail bond companies have good credit and the courts will allow you to go free if they vouch for you. In exchange you have to pay a percentage of the bail to the bail bond company.
So in our example the bail bond company may secure your release, but charge you $1,000 (10% of bail is pretty standard). You get out of jail until your trial, the jail has an assurance that you won't flee and the bail bondsman gets $1,000 - everybody is happy.
One drawback, though - if you purchase a bond you won't get any of your money back. That's right, none of it - that is the bail bond company's profit - if they gave it back to you they would not be making any money.
What if you don't show up?
So what happens if you don't show up for your court date after securing a bail bond? The bail bondsman doesn't like having to pay the court because you skipped town so they hire bounty hunters to look for you.
This sounds scary for a reason - it is. Bounty hunters thrive on their ability to track people down and they are very good at it. The last place you want to find yourself is on the run with a bounty hunter in pursuit - if you get a bail bond, don't skip town. You will be on the run for the rest of your life.
See also: Difference between bail and bond