What is Forex

Have you ever been to another country?

If you, As soon as you get down on to the air port of that country you should have to exchange your money in to the currency of that country
For an example you are from Japan and travel to Sri Lanka here you have to exchange your Japanese Yen into Sri Lankan Ruppies... If not you'll not able to buy any thing from Sri Lanka because Sri lankan shops not accept Japanese Yen . In this case you've involved in Forex Trading.FX or Forex means Foreign exchange market.
In above example you've sell Japaniese Yen and Buy Sri Lankan Ruppies
You've exchange one currency to another.
And also after comming back to Japan you should exchange Sri Lankan Ruppies into Japanese Yen

Any way Foreign Exchange Market is the Largest Finansial exchange market of the world

What is trade in forex

- answer for this question is MONEY

But the problem is we don't feel that we are buying something .. Because we are not going to buy anything physically.
Image that you are trading money in share market this is something similar to that.You buy currency from one country is same to a buying share from a company. Usually it ends up with profit if you trade properly.But there is also a risk