There are many actions you can take with your cards once you've added them to your board.
There are three contextual menus that can be used with the cards
The first is the left-click menu on a single card. To select a single card, simply left-click on a card. The options that are presented on the contextual menu vary depending on the card type.
Menu for a single-selected color card
For a color card there are 5 options, Edit, Details, Duplicate, Comment and Delete.
The details of a card give you the relevant information about that card
Duplicating a card will give you an exact copy of that card.
Menu for a single-selected text card
For a text card there are 8 options. Bold, Italic, Underline, Font, Font Size, Duplicate, Comment and Delete. For more details on text styling, read this article.
Menu for a single-selected image card
Finally, for an image card there are 5 options, Details, Duplicate, Comment, Download and Delete.
Menu for a multi-selected cards
The next is the left-click menu for multiple cards the context menu gives you 3 options, Duplicate, Spread Out and Delete. The spread-out option will equally space out all the selected cards in a linear grid fashion
Finally we have the right-click menu on either single or multiple cards which will allow you to move your card(s) forwards or backwards on the canvas
Located in the board header menu are the undo/redo buttons, which do exactly as they sound, undo will undo the last steps you have taken on your canvas and redo will put those steps back. Alternatively the keyboard shortcuts ctrl / command + z and shift + command + z perform the same function.