*This page last updated: 26 March, 2013 21:56 PST.
Units have Actions (or Orders) that they can carry out. Some are universal to all units, and some are unit-specific. Many are dependent upon the current state of the unit.
Descriptions in parenthesis are my own explanations. Descriptions in quotes are taken verbatim from the game UI.
(Move the unit to the target hex.)
Skip Turn (spacebar)
(Do nothing. The unit will awake and ask for orders the next turn.)
Wake up the sleeping unit.
"Order the Unit to remain inactive until the player provides it new orders." (Available for units that cannot Fortify.)
"Order the unit to remain in the current tile and sleep until it sees an enemy, The unit receives a defensive bonus (+25%)."
"The Unit remains inactive until the player provides it new orders. The unit receives a defensive bonus (+25%)."
(Attempt to move into the target hex and attack the enemy unit there.)
Ranged Attack (S)
(Use a ranged attack on the target hex.)
(Pillage the improvement in the current hex.)
"Garrison a unit in this city, improving its Combat Strength. This option will only appear if a unit is occupying the same tile as a city."
Embark Mode (B)
"Order the Unit to move from the land to the water." (It appears that any unit on the coast can do this. When a land unit Embarks, the unit icon changes to a five-sided home-plate shaped polygon.)
Fortify Until Healed (H)
"The unit remains inactive until it heals back to full strength. The unit receives a defensive bonus (+25%) and heals 1 HP per turn."
(Upgrade a unit to a more advanced unit, spending gold. In one example, the cost was 110 gold to upgrade a Warrior to a Swordsman.)
Set Up For Ranged Attack (S)
"Required before this unit can Range Attack." (For Siege weapons.)
Start Golden Age
"This order will consume the Great Person and initiate a Gold Age for 8 turns. Golden Ages give extra Production and Gold for the period they are active."
Conduct Trade Mission
"If the unit is inside a City-State's territory, this order will have a Great Merchant conduct a trade mission, giving you a large amount of Gold and improving relations with the City-State. It consumes the Great Person."
Found City (B)
"This order causes the Settler to found a city in its current location. The Settler is consumed in the process."
"Order the Air unit to rebase to a different city."
This order will instruct the unit to attempt an interception with any incoming air attacks and neutralize them.
Unload the unit from the boat back on to a land tile.
Launches a nuclear weapon at the chosen tile. The target and all surrounding tiles in the radius of the weapon will receive massive damage.
Order the unit to paradrop to the specified location. This mission is subject to interception.
Order the air unit to attack enemy units in the selected tile.
This will have the Great Person help research a new technology. It consumes the Great Person.
This order will hurry production on the city's current Wonder-building effort. It consumes the Great Person.
Contribute a part to the Alpha Centauri Spaceship. The unit will be consumed and must be in your Capital City to use this.
This order will consume the Great Artist and make the tile this unit is on, as well as all adjacent tiles, become part of your borders, even if they belong to another player.
Secondary Action Bar
This bar appears to contain lesser-used commands. It can be opened and closed with the button shown below.
(Open Secondary Action Bar)
"Reveals additional actions your Unit may perform."
Explore (Automated) (E)
"Order the unit to explore uncharted regions of the map. This unit will continue to move every turn until you cancel its automation.
Delete (delete key)
"Permanently delete the active unit and receive a small amount of gold in return."
Some units (such as Workers) have a separate Build Actions bar, which they can use to build Tile Improvements. For a list of buildable items, see the Tile Improvements section.
Build Citadel (C)
"This order will consume the Great General and construct a citadel improvement on the current tile."