I highly recommend you start to use google and investopedia for questions like these (not that we're not happy to help!).

Straight from Investopedia:

• Gross profit describes a company's top line earnings; that is, its revenues less the direct costs of goods sold.
• The gross profit margin then takes that figure and divides it by revenue to get a handle on how much gross profit is generated on a percentage basis after taking costs into account.
• Both of these differ from net profit or net profit margin in that net deducts several other indirect costs and expenses not found in the gross profit.