Just demoing Begin, Process, End with some pseudo-code

Show-Blocks.ps1

Function Give-UserLicense ($User) {
  #return $true 
}
Function Add-UserLicenses {
  param(
    [Parameter(
      Mandatory = $true,
      ValueFromPipelineByPropertyName = $true,
      ValueFromPipeline = $true
    )][String[]]$Username
  )
  Begin {
    # Create Session to O365 / Remote Exchange / Skype / SharePoint Session
    # This may involve prompting for / loading credentials or extended time to import modules
    Write-Verbose "Begin"
  }
  Process {
    foreach ($User in $Username) {
      try { 
        Give-UserLicense -Username $User
        $User # Output back to pipeline
      } catch {
        # Log Error
      }
    }
  }
  End {
    # Cleanup Session to O365 / Remote Exchange / Skype / SharePoint Session
    Write-Verbose "END"
  }
}
$SimpleArray = @('1', '2', '3', '4')
$ObjectArray = @(
  [PSCustomObject] @{'Office' = 'Los Angeles'; 'Username' = 'UserOne'}, 
  [PSCustomObject] @{'Office' = 'New York'; 'Username' = 'UserTwo'}
)
Function Add-UserLicensesWithoutBlocks {
  param(
    [Parameter(
      Mandatory = $true,
      ValueFromPipelineByPropertyName = $true,
      ValueFromPipeline = $true
    )][String[]]$Username
  )
  foreach ($User in $Username) {
    try { 
      Give-UserLicense -Username $User
      $User # Output back to pipeline
    } catch {
      # Log Error
    }
  }
}

Write-Verbose "Calling function that does have process block"
Add-UserLicenses -Username $SimpleArray -Verbose
$SimpleArray | Add-UserLicenses -Verbose
$ObjectArray | Add-UserLicenses -Verbose

Write-Verbose "Calling function that does not have process block"
Add-UserLicensesWithoutBlocks -Username $SimpleArray -Verbose
$SimpleArray | Add-UserLicensesWithoutBlocks -Verbose
$ObjectArray | Add-UserLicensesWithoutBlocks -Verbose

#Outputs:
# VERBOSE: Calling function that does have process block
# VERBOSE: Begin <-- notice the Begin and End blocks only occur once per call
# 1
# 2
# 3
# 4
# VERBOSE: END
# VERBOSE: Begin
# 1
# 2
# 3
# 4
# VERBOSE: END
# VERBOSE: Begin
# UserOne
# UserTwo
# VERBOSE: END
# VERBOSE: Calling function that does not have process block
# 1
# 2
# 3
# 4
# 4 <-- In this call, it only works on the last element of the collection
# UserTwo <-- Same here, it only works on the last element of the collection