Foundations
Token
A token is the basic unit of text an LLM reads and writes.
It is roughly three-quarters of a word in English, though the split varies by model and tokenizer.
Usage-based pricing, context-window limits, and latency are all denominated in tokens.
Token counts are the unit every cost or capacity conversation in this space eventually collapses to.
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Retrieval-Augmented Generation (RAG) Retrieval-Augmented Generation (RAG) retrieves relevant passages at query time and feeds them into an LLM's context. Embeddings Embeddings are numeric vectors that place similar content close together in vector space. Model-Agnostic Architecture A model-agnostic architecture lets an application swap or route between LLM providers without a rewrite. Fine-Tuning (vs RAG) Fine-tuning trains a model's weights on your own examples, changing its behavior directly.