When people refer to "Farming for Gold" or "Farming for Gear", they don't mean Gardening for these. Well, you can get gold from harvesting plants, but that's beside the point.
When people go "Farming", that means that they are taking some time off of questing to go attack a boss or two, several hundred times for specific drops. There are many different sources to get gear/gold.
A little advice, if people say something like "Want to go farm Thurnir for gold?" or "Want to go farm Waterworks for gear?", they're saying that they want to go for that boss/instance to get the gold/gear.
They mean continually beating a boss trying to get a specific gear/item/thingamajigger. You can also farm a plant, meaning grow several of the kind and try to look for a specific item like amber. Good luck!
Farming means repeatedly doing a task over and over again to gain a certain object. Example: farming for (rubies) by killing a (monster) over and over that has a high drop rate for said item. Hope that helps clear things up for you.