The "x-axis" usually refers to the horizontal axis. In Excel, that would be relevant for graphs created with Excel.
Category axis.
In classical Cartesian algebra, the x axis is defined as a horizontal number line defining the distance from a zero point called the "origin." The y axis is a vertical line defining the vertical distance from the same origin. This system has been adapted to define axes on any number of graphing systems, from Microsoft Excel to modern machine tools.
The independent variable is on the horizontal axis.
I tried creating a graph in Excel, but the x-axis always sets to the row number automatically. How do I change it?
the horizontal axis for chart is called X-axis.
The horizantal lines
It labels items on a chart. Category labels go across the bottom, on the horizontal or X-Axis. Values are normally on the Y-Axis. So if it were a bar chart, a category would have a bar coming from the X Axis and its value would be measured by what point on the Y-Axis it is equal to. The category labels tell us what that bar represents, like sales or profits or a particular year etc.
This option is available when you choose to Graph selected data in your spreadsheet. You can read Excel Help for this feature, or follow the guidelines in Google Docs to accomplish this task.
Category or Time-Scale.
posotive/ negative numbers
It is the second letter in the name of the software application Microsoft Excel. It does not stand for anything specific.