RE:RE:Kelvin Free cash flow is calculated slightly differently by different companies - it's a non IFRS GAAP metric - but in general it is the residual cash left over after all the bills are paid. If it is applied 100% to dividends then the FCF yield equals the dividend yield. If amounts are applied to other things such as buybacks the dividend yield decrases. People use the FCF yield as a what the dividend yield could be if all the money went to dividends.
Some companies include debt or partial debt payments out of FCF. This needs to be taken into accunt when comparing the FCF yields of different companies.
As for solvency. Usually when companies sell stuff the money is not received right away or a buyer may not pay. Invoices are also not paid right away. Anyway, profits don't equal FCF, think changing accounts receivable and payable amounts. I can't pay an invoice with revenues I am still waiting to recieve, only with cash. Cash flow is a solvency measure becuase it is actually how much money you received which you can then spend. A profitable company with negative cash flow will eventually be a bankrupt company.