What pants should I wear on a trek?

Go for trekking pants that are made of polyamide materials as this pants are lightweight, quick-dry, easy to clean and breathable. Apart from this, good trekking pants must be comfortable to wear and fit is really important.

Can I wear jeans on trekking?

No, you probably shouldn't wear jeans while trekking. You'll be much better off wearing a pair of trekking pants because they're lighter, more comfortable, chafe less and retain less moisture.