Funnel charts are used to show how much an item contributes to the whole. Funnel chart looks like an upside down pyramid chart.
A donut chart requires one Size Field and one Group Field. The funnel will be made from the Size Field data and Group Field determines how the levels will be split.
Please note that the Size Field needs to contain numeric fields and remember to select an Expression for this data by clicking on the field first and then choosing from the drop down.