Technically, yes, the retainer balance and trust balance are distinct. However, there are similarities as well based on the jurisdiction. Certain jurisdictions allow you to add the retainer to your operating account, while some want you to maintain it within your trust accounts, albeit you have to maintain the ledgers separately as "Retainer Balance" and "Trust Balance."
Retainer Balance: It is the money that your client gives you upfront to ensure your availability. It's like an advance payment for your legal services. You can keep this money until you actually do the work and bill for it, and the balance is available in the operating or trust account according to your jurisdiction's requirements.
Trust Balance: This money belongs to your client, not you. You hold it for things like court fees, settlements, attorney fees, or any associated and probable expenses. It has to be kept separate from your operating money to ensure it's used only for your client's needs and the total funds you've deposited in the trust account.
It must be noted that if the retainer balance is maintained within your trust account, it includes your retainer balance. Therefore, ensure adequate care to maintain separate records and highlight them separately whenever required.
So, the retainer is your money until you work for it, and the trust balance is your client's money that you're looking after.