The word "claim" is a legal term for a claim that one party has against another party. A typical claim is often a demand for payment of a sum of money, for example in the form of an unpaid invoice. But claims can also be demands to deliver a service, thing or similar.
An outstanding receivable is typically a financial receivable that has not been collected but should have been paid.
Claims are between a debtor and a creditor. In a legal sense, the creditor is the claimant - the holder of a claim, and thus the person or company that has a claim or right to a financial claim.
Purchase and sale of receivables
Some companies and collection agencies specialize in buying receivables and pledging receivables, where the creditor sells a receivable.
The sale of a debt is typically done by, for example, a debt collection company buying your debt at a discount, after which the debt collection company tries to collect the full amount. The debt collection company earns the difference between what they bought the debt for and what they manage to collect.
Receivables can thus act as a commodity or as collateral.
The sale of a receivable does not require the debtor's consent, so as a creditor you are free to sell receivables to whoever wants to buy them.
Recovery of a claim
There are many ways to recover a debt - typically with the help of a lawyer, the court, through self-collection or by using a debt collection agency.
If a debt cannot be recovered either with the help of a debt collection agency or through the enforcement court, it will be possible to file a bankruptcy petition against the debtor in order to recover all or part of the debt.
(Note: I noticed a place in the text where "Changes" should apparently be "Claims." I've corrected this in the transcribed text, but if this was an intentional wording, please let me know).