Yea, the explainer is in the accompanying "statement of facts" released by the DA: https://embed.documentcloud.org/documents/23741794-donald-trump-statement-of-facts/?embed=1&responsive=1&title=1

The claim is that DJT and Trump Org wanted to reimburse Cohen, but didn't want it on the books what they were really paying him for. So, they had Cohen send invoices monthly for a retainer agreement which didn't actually exist, and they put that on the books when they cut him the checks.

3. One component of this scheme was that, at the Defendant’s request, a lawyer who then worked for the Trump Organization as Special Counsel to Defendant (“Lawyer A”), covertly paid $130,000 to an adult film actress shortly before the election to prevent her from publicizing a sexual encounter with the Defendant. Lawyer A made the $130,000 payment through a shell corporation he set up and funded at a bank in Manhattan. This payment was illegal, and Lawyer A has since pleaded guilty to making an illegal campaign contribution and served time in prison. Further, false entries were made in New York business records to effectuate this payment, separate and apart from the New York business records used to conceal the payment.

4. After the election, the Defendant reimbursed Lawyer A for the illegal payment through a series of monthly checks, first from the Donald J. Trump Revocable Trust (the “Defendant’s Trust”)—a Trust created under the laws of New York which held the Trump Organization entity assets after the Defendant was elected President—and then from the Defendant’s bank account. Each check was processed by the Trump Organization, and each check was disguised as a payment for legal services rendered in a given month of 2017 pursuant to a retainer agreement. The payment records, kept and maintained by the Trump Organization, were false New York business records. In truth, there was no retainer agreement, and Lawyer A was not being paid for legal services rendered in 2017. The Defendant caused his entities’ business records to be falsified to disguise his and others’ criminal conduct.