If the offense is allowed to be paid online, and you do so, it is pleading guilty to the offense. If it's a moving violation, it will be reported to the Department of Driver Services and end up on your driving record.
If you go to a court, especially with an attorney, you can possibly get the charge reduced to a non-reportable offense or have the fine amount reduced.
If you want to fight the ticket and have a trial, you must go to court and plead not guilty. Your case will be continued for a jury or bench trial, depending on which one you request. Witnesses, including police officers, will not be present or required to be present at your initial court hearing.