The context block is another grouping element that can be nested inside a Describe block. You can use the Context block to denote different contexts:

function LetItSnow
{
    param ([switch]$Delightful)

    if ($Delightful)
    {
        'But the fire is so delightful'
    }
    else
    {
        'Let it snow, let it snow, let it snow'
    }
}
Describe AnotherTest {
    Context 'The weather outside is frightful' {
        $testdata = 'But the fire is so delightful'

        It 'Should be delightful' {
            LetItSnow -Delightful | Should -Be $testdata
        }
    }

    Context "Seems there's no place to go" {
        $testdata = 'Let it snow, let it snow, let it snow'

        It 'Should snow' {
            LetItSnow | Should -Be $testdata
        }
    }
}