A CCJ, also known as a County Court Judgement, is a court order that is served against you when you fail to repay money that you owe, usually after other attempts to recover debts have failed. You’ll be required to pay off your debt either in installments or in a single lump-sum.
After your CCJ has been satisfied (where no money is owed), it will still show on your credit file for six years. Which can make applying for any type of credit, including a mortgage, and other financial products more difficult because you are seen as a higher risk than someone without.
A CCJ is not the same as an IVA (Individual Voluntary Arrangement), however, it is not uncommon for both to show on your credit file, given that CCJ debt is often included in this.