How to tell if you're using 32bit or 64bit Ubuntu
Sometimes you may be asked if you want to download i386 or amd64. These stand for 32bit and 64bit respectively, and no longer have any relation to your CPU manufacturer (Intel or AMD). This is a simple guide to determining your architecture in a few simple clicks.
First you need to open System Settings. This can be done either in the dash, or by going to the gear icon (top right). From there you need to open System Info.
Under the Ubuntu Logo and Version Number, a line will list OS type 64-bit.
In this example, 64-bit is installed.
32-bit is the only other architecture you are likely to encounter and still require this tutorial.