What is meant by a primitive data type?

Question

My understanding of a primitive datatype is that

It is a datatype provided by a language implicitly (Others are user defined classes)

So different languages have different sets of datatypes which are considered primitive for that particular language. Is that right?

And what is the difference between a "basic datatype" and "built-in datatype". Wikipedia says a primitive datatype is either of the two.

PS - Why is "string" type considered as a primitive type in SNOBOL4 and not in Java ?