There is a few different way to use web data on your form. Insert from URL could be used to insert a photo or PDF into a container.
Insert From URL [No dialog; Sales::Report; “http://www.filemaker.com/sales_report.pdf”]
I have used Insert from URL to insert html in a text field from www.usps.com then I filter the information I need to retrieve the mailing address from the USPS website. I didn't have to use HTTPPOST to sent the address nor to get the mailing address returned.
HTTPPOST would be to sent a request and HTTPGET would be used to receive a request. I haven't had a need to use this because usually the URL on a website such as google maps or USPS will sent the information when you sent a address. The contacts starter solution show example of using the URL to google maps.