Ubuntu is a Linux operating system that's made for personal computers. It comes with essential applications like an office suite, browsers, email and media apps, and there are thousands more apps available in the Ubuntu Software Centre. This is open source, which means it is free to download. It's also very secure with built-in firewall and virus protection software.
The latest release, Ubuntu 16.04 LTS (Long Term Support), now provides five years of gauranteed free security and maintenance updates.