If you don’t know what a step chart looks like, it looks like the picture below. Step charts are a specialized form of line charts that use only vertical and horizontal lines to connect the data points. These charts are used when the data is not continuous in nature but characterized by a jump from one level to another. They are preferred over line charts in such cases because they form a step-like structure and bring out the intermittent pattern (the rise and fall in data) better.
While Excel doesn’t have this as an in-built chart, you can create one using horizontal and vertical error bars as shown in this post by Peltier Tech. His method creates the chart using an XY scatter chart. He also wrote this post for older versions of Excel, but it’s pretty self explanatory nonetheless.
While it’s a great post, I’ve added a custom X-axis, as due to the use of an XY scatter chart, it is impossible to show the dates in months (as shown in my picture). You can download my sample chart here.
Hope it helps.