x[t_]:=1UnitStep[t];
h[t_]:=(-Exp[-t]+2Exp[-2 t])UnitStep[t];
y=Integrate[{x[τ]h[T-τ]},{τ, 0,∞}];

Manipulate[GraphicsGrid[{{Plot[x[τ], {τ, -4,6},PlotRange->All, AxesLabel->{τ,u}], Plot[h[t-τ], {τ, -4,6},PlotRange->All, AxesLabel->{τ,"h(t-τ)"}]},{Plot[{x[τ]h[t-τ]},{τ, -4,6},PlotRange->All, Filling->Axis, AxesLabel->{τ,"x(τ)h(t-τ)"}],Plot[y, {T, -4,6}]}}] ,{t, -2, 6}]