Every single individual in the known universe has a background, his own story to tell - but who has the time to work it out for them all? Whilst players may lavish time and effort on their own characters, the GM in particular has shed-loads of NPCs to deal with... and even players may run short of time or inspiration or desire to introduce some randomness, outside factors, into the story they are writing for their character. Hence, this work.
What you get is a bunch of tables to roll on, from which you can build up as much detail as you want for an individual. First of all, there's one for the type of species the individual happens to be - depending on the availability of alien races in your universe, you may feel more comfortable picking one or modifying this to suit. Then we move on to how the individual was 'born' - anything from a conventional birth to exotic artificial methods, parents, siblings and other family members.
The next area to be explored is personal details. Quite a lot of detail on occupation, with broad categories and then sub-tables for each one; then clothing style, behaviour and even diet. Education, gender, hair colour and style... facial hair, height and weight, how healthy they are... possibly even more detail than you bother with for a character you are going to play - yet it all goes to making anyone - PC or NPC - more 'real' in the context of the alternate reality you and your friends are creating in your game. Consider this: you probably know this much about a close friend: what his favourite food is, what he looks like, what he does and a bit about how he was educated... so why do you not know the same sort of details about your character?
More details: hobbies, the sort of home the individual lives in and even how much time he spends there. Then implants - legal or otherwise - and the languages he can speak... looks, age (real and apparent), pets and personality, quirks, how good his senses are, even sexual preferences, skin colour and what his voice sounds like. Finally, there is a set of tables to allow you to create a bit of background history, a 'lifepath' if you will, of major events in his past.
It's rather fun to play with, may even suggest plot ideas and certainly leaves you knowing a lot more about a character than a few stats scribbled on a character sheet ever will!