Trade skill. What does it do?

[TheJkWhoSaysNi]

the description says it reduces trade penalty. But what is trade penalty?

Can someone tell me exactly what this skill does?

Thanks.

 

[Tarrak]

Cheaper stuff, better gains from selling... Notice how much more money you make with Marnid in tow, that is because he has 3 points in that.

 

[graphia]

It's absolutely worth dropping a point or two into Trade, it'll make a real difference to your income.

 

[sapi]

And it means that you have no reason to tow Marnid around