An arrest warrant is a court issued document directing law enforcement to take into custody for alleged crimes the person named, pending bail and/or an appearance before a judge. Custody means the local jail.
Warrants can issue without the suspect knowing. Often the warrant remains in effect until for example the person is pulled over and notified (possibly issued a summons) or picked up during a routine traffic stop or showing his/her passport for a flight. The more serious the crimes listed in the warrant, the more likely police actively will be looking for the suspect and arrest him/her anywhere anytime found. Arrest warrants can lead to searches of the person and/or property and related property seizure (and even forfeiture proceedings).
Calling the clerk of the court believed to have issued a warrant, the local jail, or the local sheriff's office will reveal whether a warrant is pending, the criminal charges, and what (if any) bail bond has been set. Assuming there is a warrant, best to have the person turn himself/herself in ASAP, early in the morning, early in the week. This will eliminate the chance of being picked up at an otherwise especially inconvenient time, and maximize the chance of not having to spend a night or weekend in jail.
The turning-in process typically goes like this: The person
walks into the local jail facility and tells reception he/she is there to clear up a
warrant. An officer/deputy will then escort him/her back into a processing room for identification, fingerprints and
photographs. The person is then held at the facility until the bond is
squared away and a court date set. At best it can take an hour or half a day,
depending on how busy they are, how staffed they are, how lazy they are, their
paperwork requirements etc. Worst case scenario could mean remaining in custody until brought before a judge either at the jail or the courthouse, or indefinitely if no bail is allowed.
Try calling the jail ahead of time to learn more about how long its process takes, the nature and amount of any bail bond, and any other particulars. Other than identification, do not bring anything else. Do not discuss the case or try to explain anything! You are there only to clear up the warrant and get your case going. If you have a lawyer or are in the process of getting one tell the jail personnel that right away. Keep your lawyer updated.
Warrants don't just go away. They need to be cleared up, the sooner the better, including so that the underlying criminal charges can be addressed and to avoid unwanted searches and seizures etc.