I saw a video that said that if you only move 1 unit you can refresh your command cards? I read in the book that you have to play a command card so I am not sure.
If by "refresh your command cards" you mean that you draw a new hand of four, then no, that is not a rule. You may, however, discard a command card from your hand during the command step to order any one unit on the board instead of playing a command card and ordering the units it says to order. This rule means you are never locked out of ordering any units and gives you a way of removing command cards that can't be used (e.g. Darken the Skies when you have no archers on the board).
In the app version of the game, you do not draw random command cards from a deck. Instead, you have 7 or so commands and once you use one, you can't use it again until you refresh your hand of command cards. The way you refresh cards is by using a specific command that lets you order one unit and refresh all of your basic command cards.
I have a feeling that the video you watched was either referring to the app, or was using a house rule taken from the app.