What is the main economy in Colombia?

I have to write a paper on Colombia and I need to know what the main economy is. I'm only in 7th grade so it doesn't need to be anything deep and political or whatever. Just like what do they make there most money from, Coffee? Crops? Minerals? and if crops or like minerals what ones? Please I have searched all over Google and can only find really complicated explanations. I'm just looking for one word answers, for example - Corn. Coffee. Timber (but what it actually is in Colombia) Thanks you so much in advance =]