You can pass variables to the parent like this:
about.blade.php
@extends('layout', ['title' => 'About'])
@section('content')
<h1>About</h1>
@endsection
layout.blade.php
<!DOCTYPE html>
<html>
<head>
<title>
@isset($title)
{{ $title }} |
@endisset
{{ config('app.name') }}
</title>
</head>
<body>
@yield('content')
</body>
</html>