The Y-axis is one of the two main axes in a two-dimensional graph, typically used in mathematics and science. It runs vertically and is used to represent the dependent variable, which is the value that changes in response to the independent variable plotted on the X-axis. In a Cartesian coordinate system, the Y-axis intersects the X-axis at the origin point, which is designated as (0,0). Each point on the graph is defined by its coordinates, with the Y-coordinate indicating the position along the Y-axis. This helps visualize relationships between variables, such as in graphs or charts.