In other words, you could think of a background as a 'backstory type' or 'backstory class'. Rather, a background represents how your backstory affected your character up to this day, when they began adventuring. It isn't a backstory on its own, but is part of it.

A background is supposed to represent the type of life experiences that your backstory has provided you. Let's start with the concept: what is it you are trying to represent? Remember that your background is not the same thing as, or a replacement for, a backstory. OK, when designing a background, you have a LOT of freedom. This content is subject to The Three Pillars of Adventure (5e Guideline). Explicit guidelines for creating a background are provided on DMG pp.289. Core character backgrounds can be found on PHB pp.127-141, and they are immediately preceded by an explanation of what they are, how they work, and how to customize them on PHB pp.123-125, starting under 'Personal Characteristics' and 'Backgrounds'.

As with everything on the wiki, please make sure that you are familiar with the precedent, which in this case is set by the 5th edition corebooks, the Player's Handbook, (PHB) Monster Manual, (MM) and Dungeon Master's Guide, (DMG). All of the design philosophies of 5th edition impact backgrounds, so they're a great place to start learning those philosophies right away, because the limited mechanics make it easier to focus on the big picture, rather than being overwhelmed by a wall of mechanical details. As a fundamentally low-powered, low-crunch element of the game, they are a great place to cut your teeth and learn control and restraint. A background can also reach a completed, balanced, functional state with the efforts of only one knowledgeable editor, though some backgrounds may take the combined efforts of 2-3 people. So, you want to make a background? Well, you're in luck because if you want to get started homebrewing character options for 5th edition, this is one of the better places to start! Backgrounds are simple, flexible, and fun! A background can be completed within a few hours if you know what you're doing, or a couple of days if you're totally new to it.

How to create your own game background