What to put as domain in setHandleParameters of gtrendsR

Question

I'm unclear what I should put as domain when setting up a proxy in gtrendsR as follows:

library(gtrendsR)

setHandleParameters(
  user = "xxx",
  password = "xxx",
  proxyport= 28,
  domain = "xxx",
  proxyhost = "xxx
)

I've read the package's manual, but it didn't clarify this for me.