The final stage of the sales funnel is the action that you're intending them to perform. In most cases this is the purchase. Again, how well you move them through the various stages is going to set you up with a specific conversion for this action. For example, if 100 people click on your offer and 10 people enter your sales funnel but only purchase people purchase, then you have a 2 percent conversion.
In marketing automation, Ryan Deiss, co-founder of Digital Marketer, often describes the sales funnel as a multi-step, multi-modality process that moves prospective browsers into buyers. It's multi-stepped because lots must occur between the time that a prospect is aware enough to enter your funnel, to the time when they take action and successfully complete a purchase.