A script is our 'unit' of work in terms of how we interact with the API. Each script is your text plus whatever sections you have plus SSML. Learn more here
An example is

scriptText="hello world"

A more advanced example of a script is the following. Note we add a sectionName and we also add in some SSML

scriptText="<<sectionName::hello>> hello world <break time = '1200ms'/> {{username|buddy}}"