Campaign influence is a feature that the consultant can recommend to measure campaign effectiveness, return on investment, and Opportunity conversion using standard Salesforce functionality. Campaign influence allows the marketing department to track how multiple campaigns have influenced an Opportunity, and assign a percentage of credit to each campaign. Campaign influence also provides reports and dashboards that show the impact of campaigns on revenue and pipeline. Campaign member, parent campaigns, and campaign hierarchy are not features that can measure campaign effectiveness, return on investment, and Opportunity conversion. Reference:
https://help.salesforce.com/s/articleView?id=sf.campaigns_influence.htm&type=5
https://trailhead.salesforce.com/en/content/learn/modules/campaign-basics/campaign-basics-influence