What Is A Template?
A template separates form from content so you can write to the Web without paralyzing your virtual pen.
To understand this, let's consider a homely piece of paper.
Papers and Forms
A piece of paper is a template or frame within which (upon which) you write words.
Blank pieces of paper make a rather intimidating template for non-writers. Even accomplished writers bite pencils, chew cigars, go for long walks and otherwise fret over such templates. In fact, many people wouldn't consider a blank page to be a template at all.
An employment application offers a far more highly structured template suited to a specific task. Borders, boxes, lines and instructions tell you where you may (or must) enter important texts. If you removed the template it would be difficult to tell what the texts meant but it wouldn't be impossible.
(Think of such items as name, address, age, social security number, past employment history).
From the point of view of the employer, the employment application separates form (the structure) from the content (what you entered into the application).
Without the template, you could still have entered all of the required content but it would have been far more difficult for you to do that and far harder for the employer to understand (maybe even find) what you had entered.
Separating Form and Content
Many templates on the Internet serve a similar - or even identical - purpose to the task-based forms you are already familiar with from daily life. Others, though, have been designed to make it easy (okay, easier) for you to design a website of varied purpose so you are not paralyzed by a blank screen.
In other words, templates offer you a structure within which you may write comfortably.
By keeping your writing separate from that structure, you can choose in the future to change a template without losing your content. (Of course, life online can be a bit more complicated than that, but this is mostly true).
While many folks experiment with templates as they grow more comfortable online so they can give their words a more personal 'look', this is optional - not required. As the Internet matures, a wide variety of attractive templates customized to a wide variety of tasks are becoming available.
Even for writers like yourself.