Opening a .backup file for PostgreSQL I'm going to warn you that whoever explains this needs to talk to me like I'm five years old, because this is something way, way beyond my level of expertise. 

In short, I have what I think is a PostgreSQL dump file that someone sent me, and I need to be able to open it up to extract the information. I was expecting a simple tabular format (such as an Excel spreadsheet), but I got something way more complicated (a .backup file). I know how to run some basic SQL queries, but I think whoever sent this to me strongly overestimated my knowledge of database programs. Could someone give me a very, very, VERY simple, completely 110% spoon-fed explanation on how to open this?

(As an aside, I know the person who sent this to me and I know the nature of the file, so I know it's not something completely different.)
You cannot just "open" a database backup. You have to restore the database. For this, you first need to install PostgreSQL. The latest version should be capable of taking backups from older versions, too. But older version may have problems with newer features in the backup. So your version should be at least as recent as the source.

How you install PostgreSQL depends on your OS that you cunningly kept a secret. In Debian it's basically a matter of:

apt-get install postgresql-8.4


(Or you take postgresql-9.1 from the backports.)

Depending on the format (there are various) you can then restore the backup. If the backup holds a complete database cluster (produced with pg_dumpall - ask your friend!), you can simply:

psql postgres -f /path/tp/file.sql


To view the data you would best use a GUI like pgAdmin. Or you learn how to use SQL. :)

For more advise you would need to provide more information. Like a short(!) sample of the backup and how it was produced.

For more about PostgreSQL start by reading the manual or one of the thousand pages on the web.

But really, your friend should just export the relevant data do a CSV file that you can open in Open Office Calc or some other spreadsheet application. Or even any text editor.