Can someone explain cost structure and market structure to me please.

These sites should help you.

http://209.85.165.104/search?q=cache:JOzqmWAuVmwJ:www.econ.washington.edu/user/brucen/300/Economics%2520300%2520au05/Economics%2520300%25208%2520(SR%2520Cost%2520Structure).ppt+cost+structure&hl=en&ct=clnk&cd=1&gl=us&ie=UTF-8

http://en.wikipedia.org/wiki/Market_form