*ToolId*                   *ProductId*

T001                       ProductA
T001                       ProductB
T002                       ProductA
T002                       ProductC

*ToolId*                 *ProductId*

T001                     ProductA; ProductB
T002                     ProductA; ProductC

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue

#Get the context
$ctx = Get-SPServiceContext https://path

#Get the scope
$scope = new-object Microsoft.SharePoint.SPServiceContextScope $ctx

#Get the target site collection
$webTarget = Get-SPWeb -identity "https://path"

#Get the Target List
$list = $webTarget.Lists["Name of List"]

#Array to Hold Result - PSObjects
$ListItemCollection = @()

#Get All List items
$list.Items |  Where-Object { $_["ToolId"] -ne ''} | foreach {
$ExportItem = New-Object PSObject
$ExportItem | Add-Member -MemberType NoteProperty -name "ToolId" -value    $_["ToolId"]
$ExportItem | Add-Member -MemberType NoteProperty -name "ProductId" -value $_["ProductId"]
#Add the object with property to an Array
$ListItemCollection += $ExportItem
}
#Export the result Array to CSV file
$ListItemCollection | Export-CSV "\pathtest.csv" -NoTypeInformation
#Dispose the web Object
$webTarget.Dispose()

$ListItemCollection | Group-Object ToolId |
  Select @{ Label = "ToolId"; Expression = { $_.Name } }, @{ Label = "Products"; Expression = { ($_.Group | Select-Object -ExpandProperty ProductId) } }

$ListItemCollection | group ToolId | select @{ L = "ToolId"; E = { $_.Name } }, @{ L = "Products"; E = { $_.Group.ProductId } }