The funnel chart is usually used to represent different stages of a sales process. Being shaped like a funnel, it's divided into different sections with each section representing a process stage. The top section represents the initial stage with most number of clients, while the bottom section is the final stage. Sections become narrower as we go down to the next stage, representing a drop in the number of clients, hence forming the shape of a funnel.

In the following example, we will take a look at how we can create a simple funnel chart:

$( '#chart_container' ).highcharts({
       chart: {
              type: 'funnel',
              marginLeft: -10
       },
       title: {
              text: 'Representing a Typical Sales Project'
       },
       plotOptions: {
              series: {
                     neckWidth: '25%',
                     neckHeight: '35%'
              }
       },
       series: [{
              name: 'Budget',
              data: [
                     ['Website visits', 56147],
                     ['User subscriptions', 21045],
                     ['Quote requests', 10423],
                     ['Invoiced', 8750],
                     ['Final sales', 8459]
              ]
       }]
});

The neckWidth and neckHeight properties in the plotOptions.series determine the width and height of the funnel's neck respectively, as shown in the following screenshot:

Hence funnel charts are useful to gain insights into the sales process and help determine the areas that need to be focused on more in order to increase sales.