Hectic. I'll say the job scope differs greatly in different industries/ positions.
As a marketing HOD, you'll be involved with many Event and Media planning, overall marketing/corporate strategy and direction, market research, product design, R&D, CRM (customer relationship management), responsible for analysing Pnl (Profit and Loss) and sales figures, budgeting, product briefings, down to public relations (internal and external), as well as in-house A&P. Also, you might get several calls a day from different publications and media owners to propose advertising packages.
Within the advertising industry, there are graphic designers, copywriters, accounts executives etc. Maybe you should narrow down your question?