And the manager can be useless, or your best friend. Basically, you give your manager orders, and your manager gives your dwarves orders.
Oh, and the manager can set workshop profiles.
Many things I wanted to add, as reading this thread, but still a while away from the most recent questions... But I'll jump in on this one.
I tend to make my manager my trader, and also be the first stonecrafter (eventually may become just one among several, in a small cohort who came with sufficient stonecrafting skills that I felt they not be wasted, then quickly become Legendary). Because stone crafts are (currently) accepted by all trading races (including elves), can be made in huge quantities (so many that you can get embarrassed by the quantities a year or two into your fortress's lifetime, if not by the first dwarven visit) and often one, two, sometimes even
three different types of rock crafts are given a premium price by the outpost liaison/diplomat.
I tend to set up one stockpile for each sub-type of craft (figurines, rings, etc), make wooden bins (or metal ones, if I have a particularly prevalent ore like lead that doesn't have a direct military application of any kind) and if I care to take advantage of the offers that the liaison/diplomat gives (could be 110-210% of their normal value) I've got easily sortable bins-worth of goods (the deal-type ones if it's the dwarf caravan, the non-deal ones if it's another caravan and I want to keep the deal-type goods for the later dwarf caravan) that I can simply send to trade and thus buy out the caravan of everything I find either directly useful, potentially useful in the future, can use for further trading, melt down to give more desired metals or am just taking off of their hands for the sake of it.
This is not necessarily something you'll want to think about in your first fort, but a manager/mayor/trader given stonecraft-only duties can do his/her bit to produce trade goods, prior to the caravan, and then be essentially forced to dedicate time to managing/trading by removing the stonecrafting duties. And forced to trade by making sure there's no Management duties. Except for he or she deciding to go to eat/sleep/drink.
There are disadvantages to all of this, but it leaves six dwarves able to do all the other things, with no worries about trading or prepping the stocks ready for the trading. And soon you'll have more migrants to fill other duties and more than enough other Legendary stonecrafters, anyway, by my experience and you'll be making half of them into haulers, for significant amounts of their time.