# LangChain & LangGraph Concepts You Should Know > Source: > Published: 2026-07-10 05:58:30+00:00 Here are five foundational **LangChain** and **LangGraph** concepts every AI engineer should understand. A **chain** is a sequence of steps where the output of one step becomes the input of the next. **Example:** ``` User Question ↓ Retrieve Documents ↓ LLM Generates Answer ↓ Format Response ``` Think of it as a pipeline for AI tasks. LLMs only know what was in their training data. **Tools** let them interact with the outside world. Examples include: Instead of only generating text, the AI can now *do things*. Memory allows an AI to remember information across interactions. Without memory: ``` User: My name is Sam. ... User: What's my name? AI: I don't know. ``` With memory: ``` AI: Your name is Sam. ``` Memory can be: An **agent** doesn't follow a fixed workflow. Instead, it: Example: ``` User: "Find the latest exchange rate and calculate how much 250 USD is in KES." Agent: → Search exchange rate → Use calculator → Return final answer ``` The workflow is dynamic rather than predetermined. Traditional chains are linear. LangGraph introduces **graphs**, where execution can branch, loop, pause, or resume. Example: ``` Start │ ▼ Understand Task ┌────┴────┐ ▼ ▼ Search Web Query Database │ │ └────┬────┘ ▼ Evaluate Results ┌────┴────┐ Good? No │ │ ▼ │ Final Answer │ │ ▼ Try Another Tool ``` This makes LangGraph ideal for building autonomous AI agents that can recover from errors, make decisions, and manage complex workflows. If you're learning modern AI engineering, mastering these five concepts will give you a strong foundation for building production-ready AI applications.