What is a workflow in CRM?

Here's an example of what a workflow might look like in CRM. When an incoming lead comes into CRM, the data has to be checked for accuracy first. Then, a sales agent has to contact a prospect, finding out his or her needs and qualifying or junking the lead.
If the lead is 'sales qualified', an office visit or remote demonstration is scheduled. After the demonstration, a quote or an invoice is sent.
Finally, an accountant has to make sure that an invoice was paid within a 30-day period. In the past, workflows used to be presented as diagrams or a chart. Nowadays, they are commonly 'encoded' into CRM.
For example, the invoice status (paid or unpaid) is automatically extracted from accounting software and reminders for overdue invoices are emailed by the system without human involvement.