To continue:
Tech tree: is where you choose what new ability you can use (left to right),by buying with science, which you get/spend by turn .
" Ya starts at the bottom, and ya works ya way up".
Agriculture is the one FREE tech you get, which allows farms to be built, after you get a worker to build a farm . Farms feed Citizens, and after a while, another Citizen is grown .
Production (hammers) is used for building things, units, buildings, Wonders; the more you have in a city, as tech's are gotten, the more you can do, and do it faster. Each city can only spend its own hammers on an in-city project; scouts, walls, shrine, warrior, archer, worker, etc.
Workers, settlers and GPeople are utterly defenseless, and should/WILL be escorted by a grunt or archer, as they can be taken or killed by Barb's or Bozo's . Dead or taken workers build NOTHING for you .
Barbarians (Barb's, Barbies) exist to ruin your day by trashing your works, farms, mines, et al; and are good for bloodying your troops for XP; I usually go Barbie hunting with 2 grunts and 2 archers, for quick kills . Clearing out a camp gets you some gold, useful stuff, that ! Granted, it takes a while to build the extra troops beyond those on escort duty; but the faster you kill Barbie camps, the more space you have to work for productions: Food, Hammers, Luxuries .
Bear in mind that troops have a ZOC (1 tile radius), which is damn useful in keeping Barb's away from your workers. A string of 3 troops, 3tiles apart, will cover with ZOC, a line of 9 tiles
(*T**T**T*), giving your peasents (oops, workers) space and time to DO work .
Scouts go out to find people, places, ruins, and can be eaten by what they find, like a Barbie camp with lots of Barbs ! ouch. Or a touchy neighbor, who thinks you're easy meat .