utility is a way to construct the resource name of an entity if you know all of
the relevant IDs related to that entity. For example, a campaign resource name
is in the format
customers/<CUSTOMER_ID>/campaigns/<CAMPAIGN_ID>, so if you
know the customer ID and the campaign ID, you can use the
utility to construct the full resource name.
$customerId contains your customer ID and
your campaign ID, you can use
to get the resource name of the campaign as shown below:
$campaignResourceName = ResourceNames::forCampaign($customerId, $campaignId)
Each entity has a different set of IDs that composes the resource name. For instance, the resource name of an ad group criterion needs a customer ID, ad group ID, ad group criterion ID.