From The Dim Future Wiki

An action is a card or section of text that represents something that can be done. Most actions are cards that can be played from a players hand onto the stack, but abilities are also actions

They have the following property in addition to the basic card properties:

Name Example Meaning
Cost 0Electric 1Protein 3Lay The energy cost that must be payed to play the action.

When an action resolves any effects in the text occur.

Many actions target a particular permanent and all actions have a well-defined source. When an action is played, the player playing it chooses a commander that they control as the source and then chooses any targets needed. The range of the action is measured from the chosen commander. (See Target and Source)

Slow Action

A slow action is an action that can only be played on a normal stack and only as the first action to be added to the stack. This means that during a turn, players in essence take turns either playing a slow action or declaring a movement stack.

Fast Action

A fast action is an action that can be played at any time the player has priority.