The first option in the Export dialog box simply places copies of all of the currently selected images into a new folder so you can copy them onto other media and share them with others. To export, select the images you want to export and then choose File > Export from the menu. This brings up the Export dialog box, where you can specify the settings for the images to be exported (Figure 1).

Figure 1: The Export dialog box allows you to specify the settings you want to use when exporting images from Lightroom.
The first section allows you to specify which folder the images should be placed in. Click the Choose button to bring up the Browse For Folder dialog box (Figure 2) and select a folder (or make a new folder), and then click OK. Select the Put In Subfolder check box if you would like the images to be placed in a subfolder within the folder you selected, and enter a name for that folder if you do want to use this option.

Figure 2: The Browse For Folder dialog box allows you to select a folder (or make a new one) where you want the exported images placed.
You can rename the files when they are exported if desired. Just remember that doing so can make it more difficult to reference the original images when the client contacts you about the images you sent them via export. The File Naming controls are the same as those found in the Import Photos dialog box.
The File Settings section contains options allowing you to control the details of the files resulting from the export process. The File Format drop-down allows you to choose which type of file you want to provide (I suggest using JPEG for basic image review, and TIFF when the images will need to be printed by the recipient).
The Image Settings section will contain controls appropriate to the file type you have selected. For JPEG, that will be a Quality slider, allowing you to balance image quality with file size. For PSD files, the only setting is for Bit Depth (8 or 16). For TIFF images, you can specify Bit Depth as well as a compression method for the files (I prefer to use None to ensure maximum compatibility, even though it results in larger file sizes). The Color Space drop-down allows you to choose the profile to be used as a color space for the images. I recommend Adobe RGB for most situations. You can use sRGB if the images are going to be used only on the Web, and ProPhotoRGB if you are sending images at a Bit Depth setting of 16. If you want to limit the size of the images (either so they can’t be reproduced very large or just so the file sizes won’t be as large), you can select the Constrain Size check box and then enter maximum values for width and height. A drop-down to the right of both fields allows you to specify the unit of measure to be used. Below this section is a Resolution field you can use to set the output resolution of the exported files.
Finally, the Post-processing section at the bottom of the dialog box allows you to specify an action that you want to be taken after the export is complete (Figure 3).

Figure 3: The Post-processing options allow you to choose what action should be taken after the export is complete.
The available options are as follows:
Note: There is also a "Go to Export Actions Folder Now" option that when selected will bring up a window showing you the contents of the folder where actions are saved.
After you’ve established all the settings as desired, click the Export button to begin the process. The images will then be processed based on your settings so you can share them with others.
For more information about Photoshop Lightroom, see the following: