This permits to create a form which will be posted somewhere, not necessarily trackers or even Tiki.
You have to find out the names of the fields of the forms that you want to send the url to.
You can use the web developer toolbar extension for Firefox or similar (see Tools for more information).
Example use cases:
you can subscribe people to an email list managed by mailan (or others list servers), providing name, surname and email from the data in the tiki tracker field.
user creation button that can be built with a users tracker. In which case field type params are
tiki-index_raw.php is the arbitrary url of the destination of the form
page:fieldname can be repeated several times, it specifies the variable names to pass in the form, as well as value taken from the current item from field named fieldname. (To be confirmed:) There is an equivalence the variable (here: page) and the content of fields with that number as fieldId.
highlight=test can also be repeated and is useful for fixed values as params to pass to the form