Install the Funnel app, specify the exact process and their stages are crucial for you in the app settings and you will get the funnel, designed solely for your business.
The most popular way of using the funnel is to control the deals' and leads' transition over the stages.
For example, you have a workflow with multiple stages / states of a project, there could be even 1000 stages in it, but you defined only 5 key stages for yourself:
Specify this 5 key stages during Funnel setup and you will get a clear picture and a table:
The funnel calculates conversions in accordance with the "how many leads made it to the current stage from the previous one" rule. This means, if your workflow allows direct leap, like "new lead > sold", bypassing all other stages on its way, the Funnel would process your data incorrectly. In fact, it would not take into account this order then.