AI/ML API provides a unified interface to access over 100 different artificial intelligence models spanning various capabilities such as chat, language processing, image generation, coding assistance, and embeddings. It's designed to offer a seamless transition for developers currently using OpenAI's services by allowing them to switch with just a single line of code change. People might want to use AI/ML API for its cost efficiency, serverless infrastructure, OpenAI compatibility, simple pricing model, and the convenience of accessing a broad range of AI models through one API, which is particularly useful for developers looking to integrate AI functionalities into their applications without the overhead of managing multiple APIs or models.