What Bhawana says is more correct than the others, but not quite.
Personnel Management originally meant to deal with day-to-day problems relating to personnel administration, payroll, trade union relations, etc. which was 'coping'; later Human Resources Management evolved, which concentrated on developing human resources, i.e. employees, through training and development, personnel appraisal, job enhancement, etc., i.e. 'developing' personnel.
Sometimes the functions are further divided, i.e. you had a Personnel Manager looking after the day-to-day 'coping' problems, a Labour Relations Officer who looked exclusively after trade union and related industrial relations problems, and a Human Relations Manager looking after 'development' issues; this is usually in large organizations where separate managers are required to look after each set of issues effectively.
However, in smaller organizations, there is usually only one single manager, called either the Personnel Manager or the HRD Manager, who himself looks after all the above issues, because he is able to do so effectively.
I hope this explains the situation a little better.
21st October 2007 From India, Mumbai