A horizontal chart is similar to a column chart with the difference that positions of dimensions and metrics are swapped with each other i.e. dimensions are on the vertical axis, while metrics on the horizontal.
Multiple dimensions and metrics are supported, and you can visualize them with different colors and move them into separate axes. You can use breakdowns in a horizontal chart as well - just not in the usual way. When multiple dimensions are chosen, then each combination of the dimensions become a separate value (essentially serving as a breakdown of the two dimensions together!).
You can eventually go deeper by adding more dimensions one by one.