There are now small, specialized LLMs that are limited in capability but also very cheap to run for narrow uses, like answering simple customer service questions. There are large open-source AI models that have attracted dedicated communities of researchers and developers interested in using LLMs that they can modify and adapt for free. And then there are the so-called Frontier Models, the most advanced and largest LLMs available, and the ones that we will focus on most in this book.
