Loading the SharePoint Snapin can be done using the following:

Add-PSSnapin "Microsoft.SharePoint.PowerShell"

This only works in the 64bit version of PowerShell. If the window says "Windows PowerShell (x86)" in the title you are using the incorrect version.

If the Snap-In is already loaded, the code above will cause an error. Using the following will load only if necessary, which can be used in Cmdlets/functions:

if ((Get-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue) -eq $null)
{
    Add-PSSnapin "Microsoft.SharePoint.PowerShell"
}

Alternatively, if you start the SharePoint Management Shell, it will automatically include the Snap-In.

To get a list of all the available SharePoint Cmdlets, run the following:

Get-Command -Module Microsoft.SharePoint.PowerShell

Print out all list names and the item count.

$site = Get-SPSite -Identity https://mysharepointsite/sites/test
foreach ($web in $site.AllWebs)
{
    foreach ($list in $web.Lists)
    {
        # Prints list title and item count
        Write-Output "$($list.Title), Items: $($list.ItemCount)"
    }
}
$site.Dispose()

Get-SPFeature -Site https://mysharepointsite/sites/test

Get-SPFeature can also be run on web scope (-Web <WebUrl>), farm scope (-Farm) and web application scope (-WebApplication <WebAppUrl>).

Get all orphaned features on a site collection

Another usage of Get-SPFeature can be to find all features that have no scope:

Get-SPFeature -Site https://mysharepointsite/sites/test |? { $_.Scope -eq $null )