You can significantly improve your Photoshop workflow by using smart objects; as the name says, a Photoshop smart object is a clever way to group one or multiple layers into one smart layer that contains inside all the other layers intact. It is easier to use smart objects simply because you can at any time edit, go back, change all the actions that you applied to the smart object. You can resize a smart object without resizing the original layer inside the smart object. You can apply a smart filter without affecting permanently the layer inside the smart object.
A Smart Object is a sum of one or multiple layers that contain image data from raster or vector images, such as Photoshop or Illustrator files. Smart Objects preserve an image's source content with all its original characteristics, enabling you to perform nondestructive editing to the layer. With other words you can edit the smart object(transform, resize, add layer styles, add smart filters, etc) without affecting the original layers inside the smart object.
For example you can add multiple sets of layer styles to a text layer without rasterizing the text. And you can of course at any time edit the text inside the smart object and also edit all the layer styles sets.
Photoshop Basix, by Adobe Certified Expert and Instructor, Martin Perhiniak includes 25 short video tutorials, around 5-10 minutes in length that will teach you all the fundamentals of working with Photoshop. Today's tutorial, Part 18: Be Smart and Use Smart Objects will define smart objects and explain how to use them.
Smart Objects are layers that store data as external sources, so you can make use of them in your document non destructively. Think about them as one file linked with a layer, so if you make any changes to the layer (rotate, distort, apply filters and effects and many other things) your source file remains intact and you can always go back to the original version, but if you change your original source it will affect all layers that point to this "file".
A Smart Object can store: Any number of Photoshop layers, including bitmap, type, shape, adjustment, and fill layers; Vector artwork created in Illustrator; An imported image file, including JPEGs, TIFFs, Illustrator files, and even PSD files. In effect, a Smart Object is like having a separate Photoshop or Illustrator document encapsulated in a layer.
If you're running CS4, you can also use the full range of Transform commands on Smart Objects.
1. Compress a bunch of layers into a single layer nondestructively. Unlike merging layers, you can convert several layers into a single Smart Object and preserve the original layers.
2. Run filters nondestructively. When you run a smart filter on a Smart Object, the filtering happens on a new layer. That way you can tweak or undo the effects of the filter.
3. Update multiple instances of the same content. If you've placed the same content in several places in your document and you make changes to the original file, Photoshop automatically updates it for you wherever it appears in your document.
4. Swap content. Once you've formatted a Smart Object just right, you can swap its contents for another image, and the new image will take on the original's attributes.