In case you are converting to or from one fo these formats, we recommend leaving the last two options ticked: doc, docx, epub, odt
In advanced options you can set things like conversion profiles and also options dealing with processing images. You can also see all the conversions that are necessary to be performed to get from your original document to the result. You don't have to worry about these conversions, as they will be performed automatically.
Profiles - You can choose different profiles in some conversions. Each profile produces a slightly different looking document(e.g. page headers, or some different styles)
Convert text only - Choose this option when you don't want your final document to contain any images. All images in the document will simply be omitted. If you wish to preserve links to images, DO NOT tick this option.
Download images - If you have external links to images on the internet in your document and you wish to include the image files in your resulting document, please tick this option.
Copy and rename images - If you choose this option, all the necessary image files you upload will be automatically included in the final document. Their file names will be changed, however.
URL for conversion with properties - This just shows what url will be the file sent to in order to perform the conversion. You do not have to worry about this, unless you would like to create your own webclient or perform the conversions with a commandline script.
URL for conversion without properties - Same as above, however this time the conversion will be performed using default properties, not the ones currently selected.