They're definitely types. Hubitat mostly follows the SmartThings model and they are types there. Also, even though it's not explicitly documented on the Hubitat side yet here is a glimpse from somebody official that this is the case:
If you don't provide a map of maps the single String or array of Strings is considered to be a type(s). You can prove this out by looking at the data types of the parameters passed to commands. For example, if you type it as "NUMBER" the parameter's type is BigInteger instead of String.
