Voluntary liquidation is when the company realizes that it is insolvent (cannot pay all debts with all its assets) and declares insolvency, resulting in liquidation. This is a legal expectation of company directors (you may not continue trading if you are insolvent, you have to liquidate).
Involuntary liquidation (the other type of liquidation) is not driven by the company but by the creditors. If they are not getting paid and believe the company is insolvent, they can apply to a court to have the company liquidated.
It obviously doesn't apply here, but for completeness, it's worth adding that voluntary liquidation can happen with a healthy company too when the owner wants to retire, for example, or there's been a sale of assets as a going concern. So not just due to insolvency.