Solicitors are allowed to take on personal injury cases on a conditional fee basis. Most personal injury actions never get as far as a court, but are settled on the basis that compensation and legal costs are paid. Solicitors can say to you that they will only expect you to pay their bill if you win. If you don't win, they will not be able to bill you. If you do win, the chances are that your bill, or most of it, will be paid by the other side anyway.
Disbursements are the things that cost money.
You may need to start proceedings in court. The court will charge a fee. Your solicitor may advise that a barrister be employed to draft paperwork or advise on your claim. The barrister will charge. These are all examples of disbursements.