URL-encoded data

what does it mean?

[fashezee]

I am setting up an online form for payments. The specifications are requesting me to send the info
as URL-encoded data. What exaclty does this mean? I have a SSL connection on the page, is this
sufficient?

[bobriggs]

Certain characters need to be escaped. For instance, spaces need to be changed to + (although %20 is acceptable). Other Characters are replaced with their hexadecimal equivalent preceded by a %.

Full list can be found here: [ietf.org...] but I'm having trouble loading the pages.

A Browser will do this automatically:
[w3.org...]