Sphere

Sphere[{xyz}]
is a sphere of radius 1 centerd at the point {x, y, z}.
Sphere[{xyz}, r]
is a sphere of radius r centered at the point x, y, z.
Sphere[{{x1y1z1}, {x2y2z2}, ... }, r]
is a collection spheres of radius r centered at the points {x1, y2, z2}, {x2, y2, z2}, ...