Network build and service delivery can take many years, requiring significant long term funding. Budgets detail how much is needed, and sufficient funds raised - by share or loans. Cash Burn is the net cash consumed or 'burnt' each month and when compared to the funds still held gives the time you have left using your current cash resources. Typically quoted as 'we are fully funded until December 2003'.
I have a large pot of money, and I'm spending it fast. I hope to generate some money in future - but when that begins is uncertain. So how many months can I survive at the rate at which I'm burning cash? After that time I'll need some more if my business is to survive.