My friends and relatives (those ignorant about the software industry) are curious to know how I work in a software company without being an engineer. It puzzles them no end. I patiently give them an explanation that I am a writer who documents software. Hence, I justify, the emphasis is on writing skills and not my engineering/coding skills. My favorite example is the refrigerator manual. I tell them that just like a manual for any consumer durable (like a fridge), I write manuals for software. They nod politely so as not to look stupid, but I know its still Greek and Latin to them.
Some of the following points may help them understand this profession better.

All technical writers are NOT engineers
Technical writers need not be engineers. Any graduation degree is fine, provided they have good communication and writing skills. Technical writers need to have an open mind to learn new technology. At the start, technical terms may give you that uneasy feeling in the stomach that happens when you fear something. Not to worry, you will get a hang of it gradually.

Some engineers are technical writers
Some engineers have a flair for writing. For writing API manuals, Instruction manuals, engineers have an added edge. This is not to say that non-engineers cannot do the job. But with some exposure to how code is written or how the backend works, the engineers’ grasp maybe faster. Some companies explicitly ask for an engineering background when they advertise for technical writers.

What do engineers do in development?
Engineers develop software. They write code to make a software work, to get a specific job done for e.g., Online booking of train/air/bus tickets, online payment gateways etc. They decide on the logic behind the software, what, how and when each component/feature in a software works.

What do engineers do in QA?
The Quality Assurance engineers check the working of the software developed by engineers. They do load testing to check how many customers/hits the software can handle at a time. They report any malfunctions (bugs) in the software which is eventually fixed by the developers. They also test the usability of the software.

How “technical” is a technical writer?
A technical writer need not be a person with a technical background, but definitely needs to understand the technology used by the company. They need to understand how the software works by navigating through the user interface (UI) of the software. Only when they understand the flow of the software can they document the steps to use it. In many ways the technical writer also tests the usability of the software by using it from the customers’ viewpoint.

Also a technical writer has to know how to use tools to document software, like MS Word, Framemaker, Madcap Flare etc.

Writing skills of a technical writer
The most important skill that is an absolute must for a technical writer is his/her writing skills. The tech writer has to document the software keeping in mind the customer. Writing has to be precise consistent and user friendly, so as not to confuse the user.