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.
If you're wondering what a sales funnel is, simply imagine a real-world funnel. At the top of that funnel, some substance is poured in, which filters down towards one finite destination. In sales, something similar occurs. At the top, lots of visitors arrive who may enter your funnel. However, unlike the real-world funnel, not all who enter the sales funnel will reemerge out from the other end.