What is the trans-atlantic slave trade

Hello!  To answer your question of what the trans-Atlantic slave trade is, we can break it down.  

1) trans, what does the prefix mean? Can you think of any other words in which it is used, and can you then apply your knowledge of what the prefix then means?  Think of transcontinental railway, or something of similar.

2)Once you know what trans means, this should come pretty easy, what does Atlantic refer to? 

3)The last part of your question would be to answer, what is the slave trade?  I'm presuming since your looking at the trans-Atlantic slave trade, you're already informed about what slave trade is. If you aren't, think of the two words.  Slave, and trade.  What, or who were slaves, and what is trade?  When you trade, what do you do? 

I hoped this has helped, and if you have any further questions pertain to this question, just shoot me a message or another question.  Good luck :)