If you’re reading or talking about Linux, you might hear people use two new words: distribution and kernel. Every operating system is built off of a kernel, which is the core of the OS, doing most of the hardware management. Linux is a collection of a kernel and a few other things, not necessarily organized well together like Windows or Mac would be.
A distribution gathers all of those components in a specific configuration – like you’d expect from Windows or Mac – and puts them together in an easy to download and use package. The most popular Linux distribution (distro for short) is Ubuntu.