VectorPlot[{x,y},{x,-2,2},{y,-2,2}]

VectorPlot[{-x,-y},{x,-2,2},{y,-2,2}]

VectorPlot3D[{x^2y,Cos[z],Sin[z]},{x,-2,2},{y,-2,2},{z,-2,2}]

VectorPlot3D[{x^2,3x z^2,-2x z},{x,-2,2},{y,-2,2},{z,-2,2}]

Show[
RegionPlot3D[Abs[x]<1&&Abs[y]<1&&Abs[z]<1,{x,-1.5,1.5},{y,-1.5,1.5},{z,-1.5,1.5},PlotStyle->Opacity[.5]],
VectorPlot3D[{x,y,z},{x,-1.5,1.5},{y,-1.5,1.5},{z,-1.5,1.5}]
]

Show[
RegionPlot3D[Abs[x]<1&&Abs[y]<1&&Abs[z]<1,{x,-1.5,1.5},{y,-1.5,1.5},{z,-1.5,1.5},PlotStyle->Opacity[.5]],
VectorPlot3D[{x y, y z,  y^2z},{x,-1.5,1.5},{y,-1.5,1.5},{z,-1.5,1.5}]
]

Show[
RegionPlot3D[Abs[x]<1&&Abs[y]<1&&Abs[z]<1,{x,-1.5,1.5},{y,-1.5,1.5},{z,-1.5,1.5},PlotStyle->Opacity[.5]],
VectorPlot3D[{-y,x,0},{x,-1.5,1.5},{y,-1.5,1.5},{z,-1.5,1.5}]
]

Show[
RegionPlot3D[x^2+y^2+z^2≤1&&x≥0&&y≥0&&z≥0,{x,0,1},{y,0,1},{z,0,1},PlotStyle->{Opacity[.5]}],
VectorPlot3D[{x^2y + y^2 z,x y^2, x^2+y^2},{x,0,1},{y,0,1},{z,0,1}]
]