Invoice factoring is a financing method where businesses sell unpaid invoices to a third party (factor) for immediate cash, typically advancing 70% to 90% of the invoice value. There are several types of factoring, including recourse, non-recourse, spot, and whole turnover factoring, each with its own advantages and disadvantages, such as improved cash flow and potential customer relationship strains. When choosing a factoring company, businesses should consider reputation, fees, flexibility, and customer service.