I once interned at Schlumberger, a company that describes this as "Internships That Don't Involve Photocopying". It was great in the sense that I was put with extremely experienced engineers and some nuggets have stayed with me.
I was helping an engineer when he was cleaning some tools and tagging them as part of a procedure. We were talking about the task at hand and I asked him if he found it boring. He said "It is boring, the most boring part of the job. But it's also the most important. You clean, calibrate, and tag the tools so that the next time a job comes, you or someone else know the tool is good and has been checked.".
When I joined my current company as an engineer, I thought about it in terms of documentation and knowledge dissemination so other contributors or my future self may benefit and I had started a technical knowledge base.
Now I'm COO (and CTO by interim: first CTO quit, subsequent CTO doing military service), we make sure to include new team members in communication with clients (emails, calls, or meetings), invite them to contribute to the exchange, involve them in the whole process of making the product, from elicitation to business viability of a feature and engineering trade-offs, to running the company and the business side of things. Many of our engineers are still students and have been with us for years, and we're doing this in the hope that they learn how to make products and run companies that would die otherwise, as opposed to be in companies that'd do well regardless of their presence. They learn to operate with a broader range than only fixing bugs (but still managing to fix the darn bugs).
I then started an "Operations" knowledge base called "Operator's Manual" shared on GitLab. I put in all the things I had to learn how to do as I took over so we wouldn't have that problem again if something happens to me or I'm fired and any employee can pick up the thing and be able to somewhat operate the company and have a starting point.
It has information about the company, hiring (from how to receive a candidate and asking if they'd like something to drink to onboarding), firing, taxes and how and where to pay them, invoices and the legal texts they must comply with, etc.
It became a "Handbook" that is augmented as we continue to learn things and build an organization. You can imagine how delighted I was when I found out that GitLab had such a handbook on GitLab on how GitLab is run : )