Labor = money. Period. There are very few ways to make money outside of using labor. Labor is used in everything from opening coin purses from mobs to crafting.
You gain 10 labor every 5 minutes for a total of 2880 labor every day.
In other games you’d compare your income by saying “I make X gold per hour.” In Archeage it’s “I make X silver per labor.” (silver/labor, s/l, etc.). You could farm mobs for 10 hours straight, but you’ll still have to wait for your labor pool to recharge before you’ll make any gold from them.
The general rule of thumb is to try to earn more silver/labor than you would from opening coin purses from Auroria mobs. This is about 4 – 4.5 silver/labor (before any proficiency bonus). That equates to around 3,500 gold per month if you ONLY open coin purses and don’t own land.
If what you’re about to spend your labor on isn’t at least breaking even with coin purses, then it’s probably not worth doing (unless you’re after something specific, using an alt account, want to be lazy and afk process materials, or just don’t care.)