The main viewing window is divorced in 3 sections. The large right part is where you move your units. The bottom left-hand section is information about the active unit and the section to the upper left is a map over the whole world. Because there is so many things to build in the cities and it is tiresome to look them all up in the manual there is included a civilopedia where you can read all about the buildings, units, wonders of the world and landscape types. It not only includes attack and defence information it also explains when and why for example the barracks were invented.
Every building has it owns advances.
Every building you have cost some money every turn in maintenance and that amount is subtracted from the Treasury . If the treasury is empty a random selected building is sold and the amount is put in the Treasury. You can also use the Treasury to buy new buildings in one turn. There's five type of governments you can have. You start with despotism and as you invent monarchy, republic, cummunism or democracy you can change government.