Adobe's help:
JPEG uses a standardized image compression mechanism to compress full-color or grayscale images for onscreen display. Use the Export command to export a page, spread, or selected object in JPEG format.
- If desired, select an object to export. (You do not need to select anything to export a page or spread.)
The Export JPEG dialog box appears.
Selection
Export the currently selected object.
Range
Enter the number of the page or pages you want to export. Separate numbers in a range by using a hyphen, and separate multiple pages or ranges by using commas.
Select All
Export all pages in the documents.
Spreads
Export facing pages in a spread to a single JPEG file. Deselect this option to export each page in a spread as a separate JPEG file.
Maximum includes all available high-resolution image data in the exported file and requires the most disk space. Choose this option if the file will be printed on a high‑resolution output device.
- Low includes only screen-resolution versions (72 dpi) of placed bitmap images in the exported file. Choose this option if the file will be displayed onscreen only.
- Medium and High include more image data than Low, but use varying levels of compression to reduce file size.
Progressive displays a JPEG image in increasing detail as it is downloaded to a web browser.
- Baseline displays a JPEG image after it has been downloaded completely.
Embed Color Profile
When this option is selected, the document’s color profile is embedded in the exported JPEG file. The name of the color profile is displayed in small text to the right of the option. You can select the desired profile for the document by choosing Edit > Assign Profiles before exporting to JPEG.
If Gray is chosen from the Color Space menu, the Embed Color Profile option is disabled.
Use Document Bleed Settings
If this option is selected, the bleed area specified in Document Setup appears in the resulting JPEG. This option is disabled if the Selection option is chosen.
Anti-Alias
Anti-aliasing smooths the jagged edges of text and bitmap images.
Simulate Overprint
This option is similar to the Overprint Preview feature but works for any of the selected color spaces. If selected, the JPEG file that InDesign exports simulates the effects of overprinting spot inks with different neutral density values by converting spot colors to process colors for printing.