Description of a RPE variable, what is the function/purpose of "publishParameter:true"?

In Rational Publishing Engine, users can create variables with an Access value of external or internal. Additionally, users can specify a Description. It is to my understanding that the Description is used as the display value of a variable within the Additional Report Information step of the Create a Document-Style Report process.
Accepted answer

If my understanding is correct, setting "publishParameter:true" does not change the display name. Rather it will be supplied (appended) as parameter with the request URL.
For example, OOTB template printModuleBook.dta contains variable "showAttributes" with Description set to "Include Attributes(publishParameter:true,type:boolean)". The display name (in DNG web UI) will be "Include Attributes" which can be set to true or false. ?showAttributes=true or ?showAttributes=false will be appended to the request URL during document generation. Similarly, printArtifact.dta has variable footerText, for which description is "Footer Text(type:text)". Hence we see "Footer Text" in the report wizard, which accepts text value.
Access value does not matter if you are generating document through DNG. If the name is prefixed with "_", it will be hidden from the report wizard.
"Central Library Variable" can be ignored since it is no more relevant.