Under common law, an "accord" is an agreement to settle an undisputed obligation with some sort of performance that differs from the original obligation.
This is different from a "settlement" or "compromise," which resolves an outstanding dispute. An "accord" resolves an undisputed debt.
The legal distinction between the two is this:
When a settlement is agreed to, the performance agreed to in the settlement becomes binding upon the parties instead of the original obligation. For example, let's say A claims $4,000 from B, and B disputes this amount, but agrees to settle the dispute by giving his computer to A. If B never pays up, A can only recover the fair market value of B's computer: he is barred from raising his original claim of $4,000 because the settlement superseded the original obligation.
In contrast, an accord gives the debtor the option to perform their obligation with the "satisfaction" agreed to in the accord, but if they fail to do so, their creditor can still claim the original amount. So in the above example, if B did not dispute the amount of the debt but offered to "settle" it by giving A his computer, and A agreed to this (forming the accord), A could respond to B's default by either suing for the value of the computer (the amount of the accord) or suing for $4,000 (the original obligation).