Hi Mybloodykids, I did the same as cookiepuss and asked my consultant about this, because my friend was having chemo before surgery, while the plan for me was to have a mastectomy possibly followed by chemo.
Chemo after surgery is a mop-up effort to get at any remaining breast cancer cells, including those that may have escaped the lymph nodes -- an 'insurance policy' as some doctors describe it.
Chemo before surgery might be given to help shrink a large lump enough to allow for less extensive surgery. For example lumpectomy + radio rather than a mastectomy. It also helps assess how well a chemo regimen works, because they can monitor the size of the lump to see if it shrinks. Some usual scenarios for giving chemo before surgery are: if going straight in with surgery is unlikely to be successful in removing all existing disease; or if there is ER-negative, HER2-positive or triple-negative disease. As argy said though, there's a lot of different factors to consider and the recommendation is not based on one or two things alone.
Some people can have both.
Reassuringly I thought he said studies show there is no difference in survival, or in the chances of breast cancer recurring in 10+ years, with chemo given before (neoadjuvant chemotherapy) or after (adjuvant chemotherapy) surgery.
Your MDT (multidisciplinary team -- my consultant kept saying 'let's set your next appointment after the MDT' so I had to look it up; I only ever see him though and the BC nurse) will discuss which approach they would recommend for you. Or in your case, you can ask for more info on the reasons behind plan.
I had ER-positive (8/8), HER2-negative BC, which would be more likely to respond to slower acting hormone therapy with tamoxifen, so was an unlikely candidate for chemo before surgery. With small sites (no one could feel any lumps) scattered through my boob, doing a mastectomy straightaway made sense. Consultant said because my boob was so small there wouldn't be much left anyway if they tried breast conserving surgery 
With my friend, she had such a complete response to chemotherapy that after her surgery she didn't need to have more chemo, so a great result for her.
Sorry lots of people are going through a crap time
Thinking of you all.