When you move or copy items between Galleries in the same catalog, nothing about the individual item records in the database changes—you are merely creating different ways to isolate and view cataloged items.
To Copy items between Galleries in the same Catalog:
Open a Saved Gallery, or create a
new Gallery; [choose Window > New Gallery, or click the New
Gallery button 
on the Toolbar,
or press Command+G (Mac OS) or Ctrl+G (Windows).
From the originating Gallery, select the item(s) that you want to copy. To select all the items in the Gallery, choose “Select All” from the Edit menu, or press Command+A (Mac OS) or Control+A (Windows).
Drag and drop the items into the target Gallery window.
— or —
With the items in the originating Gallery selected, choose “Copy” from the Edit menu [Command+C (Mac OS) or Ctrl+C (Windows)].
Activate the receiving Gallery window by clicking it, then choose “Paste” from the Edit menu [Command+V (Mac OS) or Ctrl+V (Windows)].
The items will be copied to the new Gallery.
To Move items from one Gallery to another:
Open a Saved Gallery, or create a new Gallery [choose Window > New Gallery, or click the New Gallery button on the Toolbar, or press Command+G (Mac OS) or Ctrl+G (Windows)].
In the originating Gallery, select the items that you want to move. To select all the items in the Gallery, choose “Select All” from the Edit menu, or press Command+A (Mac OS) or Control+A (Windows).
Choose “Cut” from the Edit menu [Command+X (Mac OS) or Ctrl+X (Windows)].
Activate the receiving Gallery window by clicking it, then choose “Paste” from the Edit menu [Command+V (Mac OS) or Ctrl+V (Windows)].
The items will be removed from the originating Gallery and added to the receiving Gallery.
Note: Even if you do not paste the items into another Gallery, they are not deleted from the Catalog.
See also:
Gallery - Customized Gallery Views