when you factor work out, what in means is another company is 'buying' invoices off you.
say for example you were sending invoices out for �1000pw, and then having to wait for payment and chase them up.
the 'factors' an outside company, may say to you i'll give you �900 today. it is up to them to chase your customers, its them that is now owed the money.
or they may say we'll invoice the customers and chase payment, and once we get paid we'll pay you. but may only pay you �950.
don't know how much they charge, the figures are only examples, but i think it is a pretty common practise, especially with small firms who may have a cash flow problem.