Personal licences are for home use on personal projects and can only be purchased as single licences. Typically this would be for hobbyists, etc.
Business licences are for when purchasing for a business or organisation and can be a single licence
or multi licence to cover multiple PCs. If you require a company invoice and/or an EU VAT invoice, then you would need an Business licence.
If I pay the $99, how many PCs can I put it on? Or do I have to pay more money to put it on multiple PCs?