RegionPlot

RegionPlot[pred, {x, xmin, xmax}, {y, ymin, ymax}] makes a plot showing the region where pred is True.

Examples

Plot a circular region:

RegionPlot[x^2 + y^2 < 1, {x, -1.5, 1.5}, {y, -1.5, 1.5}]

Multiple regions:

RegionPlot[{x^2 + y^2 < 1, x + y < 0}, {x, -2, 2}, {y, -2, 2}]

Please visit the official Wolfram Language Reference for more details.