Ask a cold assistant to "write a follow-up email" and you get something generic. Tell it you are a logistics account manager, the client is annoyed about a late delivery, keep it warm but firm, three short paragraphs, and you get something you could almost send. Same request, night-and-day result, and the only thing that changed was the context.
ChatGPT adds a twist. Unlike a tool that starts every chat from zero, ChatGPT remembers. With memory on, it can draw on your past chats, things it saved about you, your custom instructions, your files, and connected apps. That is a head start, and it is also a responsibility: context you never meant to give can shape an answer too. This lesson covers both halves, giving context on purpose and keeping an eye on what it remembers.
Give it the material
The most direct context is the stuff you already have. Upload it with the + button in the message box: PDFs, Word and PowerPoint files, spreadsheets, text, and images. The limits are generous (files up to 512 MB, documents up to about 2 million tokens, spreadsheets around 50 MB, images 20 MB), so the real report, the actual spreadsheet, the brief you were sent all fit.
If an answer depends on a document, hand ChatGPT the document. Do not retype it or describe it from memory. Give it the real thing and ask your question about it.
On formats, lean wins. Plain text and Markdown carry the same words as a heavily styled Word file with none of the overhead, so when you control the format and will reuse the material, a .md or .txt file is the cleanest choice. When you do not control it, upload what you have. Any source beats no source.
What ChatGPT already remembers
With memory switched on, ChatGPT keeps two kinds of context. Saved memories are details you asked it to keep ("remember that I write for a non-technical audience") or that it saved as useful. Chat history lets it pull in relevant bits of earlier conversations, and that picture updates as you go. ChatGPT decides what is relevant for each answer.
You stay in charge, and three habits keep it that way:
Look at the sources. Under an answer, memory sources can show what influenced it. If something old or wrong crept in, you will see it there.
Correct or delete. In Settings, Personalization, Memory you can read a summary of what ChatGPT keeps, correct it, delete items, or turn memory off. Note that deleting a chat does not delete a saved memory that came from it; delete the memory too.
Go clean when you need to. A Temporary Chat is not saved and does not create memories. Choose Unpersonalized before you start and it also ignores your existing memories and instructions. Handy for a one-off task that should not colour the rest.
Context isn't unlimited
All of this lands in ChatGPT's context window: what it can hold in mind while it answers. It is large but finite. The files you add, the conversation so far, and the reply being written all count. Long, wandering chats and heavy files fill it, and detail starts to slip.
So the habits from lesson 2.2 pay off twice: one topic per chat, a fresh chat when you switch tasks, and lean material. Part 4 opens with the full mechanics.
Three places to put context
Context can live at three levels, from "just for now" to "for good". Picking the right one saves you from repeating yourself.
This message. Paste or upload context where you need it. It lasts for this chat. Perfect for a one-off: "here's the report, summarise it."
This project. A project groups chats, files, and instructions for a piece of ongoing work, and its instructions apply to every chat inside it, overriding your general ones. That is a Part 4 topic.
Everything. Your custom instructions (Settings, Personalization) apply to every chat. Next to them, Base style and tone sets the overall voice, from Professional to Efficient. This is where your durable facts live: your role, how you like answers, terms your sector uses. Rule of thumb: the more often you would retype something, the wider you should set it.
Write a short brief once
The best ten minutes you will spend in ChatGPT: write a short brief about how you work and put it in your custom instructions. A handful of lines that answer who, what, and how. Something like: "I'm a marketing lead at a mid-size logistics firm. I mostly write client updates and internal briefs. My readers are busy and non-technical. I like a warm, plain tone, short paragraphs, no jargon. Never invent figures; ask me if you're unsure." Paste that once and every answer starts closer to right.
One caution, straight from lesson 1.4: context is powerful, but the rules still apply. Confidential work belongs in your company's Business workspace, where it is not used for training. On a personal account it is, unless you switch training off.
Where this goes next
Context tells ChatGPT who it is helping; the prompt tells it what to do. Part 3 is all about the prompt. In Part 4 your brief grows into projects and skills, reusable ways to give ChatGPT context and behaviour on tap. For now the habit is enough: never make ChatGPT guess what you could simply tell it, and now and then, check what it thinks it knows.
Try it
Write your own brief, about your real role, in under a hundred words. Open Settings, Personalization and paste it into your custom instructions.
Then open the Memory summary in the same place and read it. Is anything outdated or wrong? Correct or delete it. Finally, start a fresh chat and ask for something you actually need, like a short update to your team. Notice how much closer the first answer lands, and check the memory sources to see what shaped it.
(General exercise. Role and industry versions come once accounts are in.)