How LLMs Work – Deep Technical Overview

Last updated on August 12th, 2025 at 12:37 pm

Updated August 2025 for GPT5 / Gemini 2.5 Pro

Have you ever explored how llms work? If not, how can we talk of AEO and GEO and so on? Most marketing strategies today are still based on metaphors that no longer apply. Terms like “ranking,” “indexing,” and “domain authority” may be appropriate for search, but they have little meaning in the architecture of a Large Language Model.

This is where things get technical. While it might feel overwhelming at first, I encourage you to read slowly, pause, and let the ideas settle.

To influence a system, even indirectly, you need to first understand how it works.

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Access the full Research Paper. For free.

This article is just an extract from the full 100 pages independent research I’ve written for Fuel LAB® Research over 2 years of analysis, studying LLMs models, and data collection.

Unlike traditional search engines, LLMs like GPT-5, Claude 4.1 Opus, or Gemini w.5 Pro / Flash do not retrieve web pages and choose the “best one.” Instead, they generate answers word by word based on patterns learned during pre-training, shaped during fine-tuning, and generally enhanced by real-time tools like search or code interpreters.

This chapter explains how that process works:

  • How LLMs are trained
  • How they encode language and meaning
  • How their internal structure allows emergent abilities like attempt at reasoning, planning, and memory-like behavior
  • Why outputs are fluent but unpredictable
  • And why direct optimization is impossible, but indirect influence is probable.

We’ll cover key concepts such as embeddings, self-attention, transformers, token prediction, and reinforcement learning with human feedback (RLHF).

We’ll also demystify why LLMs “sound smart” even when they’re wrong, and how the illusion of reasoning emerges from statistical computation.

A chart showing how llms and ai predict the next token

Picture credit: Rateb Al Drobi, https://www.linkedin.com/posts/rateb-al-drobi_post-410-how-llms-actually-generate-text-activity-7300199524680032256-njGZ/

This collection of posts will also include references to retrieval-augmented generation (RAG) and multi-modal capabilities, as many LLMs now use external tools (search, calculators, code) and work with not just text, but images, audio, and even video.

Here below you can find the posts that have been written by extrapolating from the full research paper. For your convenience, here’s the natural order of the articles and how they should be read:

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