This blog introduces the fundamentals of CLIP, an advanced text-to-image service developed by OpenAI. It explains how search algorithms and semantic similarity are used to match texts with images. The process involves mapping the semantics of texts and images into a high-dimensional space where vectors representing similar semantics have small distances between them. A typical text-to-image service consists of three parts: request side (texts), search algorithm, and underlying databases (images). CLIP helps in creating a unified semantic space for both texts and images, enabling efficient cross-modal search. The next article will demonstrate how to build a prototype text-to-image service using these concepts.