What is mean by free form in data type under variables in catalog item form

[Ankita Singh2]

What is freeform here 

[Miguel Donayre]

The picture looks like a requirement(s) from someone, and I would ask the person who wrote it to see what they meant. A "string" type field could allow the end-user to enter some text into a field.

https://docs.servicenow.com/bundle/rome-platform-administration/page/administer/reference-pages/refe...

[Vinayak Belgaon]

In your case the free from field type would mean a string type, so either it can be a single line text or  multiline text for variables

Regards

Vinayak