Ranking
Journal ranking comes from ISI impact factor (Thompson Scientific). Lets say you have published an article in Journal A. That journal A will belong to a field or may belong to multiple fields, if it is multidisciplinary. Based on the impact factor (which is journal specific and field independent), Journal A can be ranked as #5 in one field but #30 in another field. More importantly, #5 out of 7 journals may not be as good as as #30 out of 400.
Citations are more specific to your article... and that does not depend on the impact factor. Those citation details will come different citatin indices.
Hope that answer your question.