(Mr. Geno's advice about Texas law is way off. He is not licensed to practice in Texas according the State Bar, so I would value his words accordingly.)
A personal bond under Texas criminal law is a release from jail with the promise to appear at all future court dates. The defendant does not have to pay any money to secure this bond, although some counties Pretrial Services offices do charge a small fee. If the defendant fails to appear in court when scheduled, then the bond can be revoked and the defendant agrees to pay the county the amount of the bond. Contrary to Mr. Geno's advice/attempt to solicit business for a friend, you do not have to hire a bonding company to get a personal bond in the State of Texas.
Listen to Paul, not Brian. Brian is not licensed in Texas. Paul is. I am.
In Kaufman we call a personal bond a personal recognizance of PR bond. It is a promise to appear in court that does not require a cash payment or surety.
Basically, the defendant promises to show up for future court proceedings. Whoever it is we are talking about needs an attorney to assist. I know you are looking for information, but without a lawyer to litigate this issue you can not help this person.
Remember, this is avvo, not legal advice. I am not your lawyer, you are not my client.