about publicly traded companies

I still don’t get it though I wrote the exam yesterday and I could work out share problems a bit.

Say a company has 100 shares when first incorporated, so each of the 100 shares accounts 1% of the company’s ownership, or accounts its net assets?

Then, during the IPO, all of the shares will be offered, or a portion of it, say 30 shares? Then, the price of each share times total share amount, which is 30 in this case, accounts for 30% or 100% of the company’s market value?