Tax, unlike audit, is mostly based in your own office - i.e. you will sit at your desk every day at the Deloitte office rather than visit clients. On a day to day basis, your job will initially begin with doing the mundane stuff- checking company tax returns, performing tax audit work for the audit service line - that sort of thing. There will also be a lot of studying to do, and you will be given tax training that goes above and beyond the ACA training.
It’'s mostly spreadsheet work, so don’t get too excited!
As for why you want to do tax, well, only you can answer that! I can give you one piece of advice though - some people suit tax, and some do not. If you like attention to detail and always like to get things right, and follow methods and procedures, tax is for you. If you are a bit of free spirit, you are probably better suited to something else.