You can also put custom variables in the front matter. These can be reused in the page layout.
For example, if your front matter looks like this:
---
layout: post
title: "Using Custom Variables!"
date: 2016-07-25
chicken: "I like Chicken."
---
You can use the chicken
variable in the post layout like this:
<!DOCTYPE HTML>
<html>
<head>
<title>{{ post.chicken }}</title>
</head>
<body>
...
The chicken
variable will be substituted in instead of {{ post.chicken }}