Under factoring the lender takes over collection: it chases your customers, allocates the payments and manages the sales ledger. That suits a business without a credit control function, and it is visible to your customers. Under invoice discounting you keep collecting, and on a confidential facility your customers are not told there is a lender behind you. Discounting is usually reserved for businesses with stronger systems and a longer record.
The advance is a percentage of approved invoices, commonly around 85% to 90%, with the balance paid over when the customer settles, less the charges. Invoices that are disputed, outside terms, or owed by a debtor the lender has not approved do not count towards availability, which is why the real facility size is a function of your ledger rather than of your turnover.
Concentration limits matter more than most owners expect. A lender will usually cap how much of the facility can rest on any one debtor, often somewhere around 25% to 40% of the ledger. A business with one dominant customer can look well funded on paper and find availability far lower in practice, so that is checked before an application rather than after.