Joined is an option for ListPlot and related functions which specifies whether points in each dataset should be joined into a line, or should be plotted as separate points.
Joined->{s1, s2, ...} specifies separately whether to join each dataset. If there are more datasets than si given, the si are used cyclically.
Joined->True specifies that a line rather than points should be drawn. The additional option Mesh->Full specifies that the original points should also be indicated.