There isn't a specific name that describes this as an individual cipher. It is indeed a "Caesar cipher" that merely differs from the cipher Julius Caesar himself used as it uses two (or more) numbers to shift the alphabet. Looking at your description a bit closer, one could maybe even think it is somewhere half-way between a Caesar cipher and a Vigenère cipher. But from my point of view, it's nothing more than a Caesar cipher derivate.
Actually, the link you provided already tells you it is merely a Caesar cipher by stating in bold letters:
Interesting fact: the Roman Emperor Julius Ceaser used this method to hide his secret messages!
Now, as for the cryptanalysis… this may be harder to break using pen-and-paper, but in the end it has the same problems as the classic original and a bit of frequency analysis makes it possible to recover both the used "key" as well as the plaintext. Especially, when using computers to analyze.
"is it trivial to break?" Yes! Caesar ciphers, Vigenère ciphers, and alike classic ciphers are all pretty easy to break. Meaning: Do not use such antique, classical ciphers for anything serious!
Yet, I'm wondering why you're asking… because the link you provided already states the same:
As I said, a computer can break this code by working out what would happen for each of the code numbers and checking the resulting message against a dictionary to see if the words it has created are real words. Because it can work this out very quickly it can break the code quickly.
The Wikipedia article related to the Caesar cipher dives into the cipher, it's variants, and it's security problems it a bit more detailed. You might want to take a look at it… and while you're at it, check out the Wikipedia article related to the Vigenère cipher too as it might be interesting for you too.
Also, for a more practical view on those two ciphers, it might be interesting for you to check on sites like…
Nota Bene: There are others alike sites out there too, but I simply happened to have these links handy.