The majority of campaign execution occurs outside of Salesforce. It can be online such as with email vendor or offline such as at a trade show. Marketing cloud?
The Campaign standard object can be customised to fit whatever marketing strategy the organisation is using. You can add leads and contacts to a campaign as campaign members.
The campaign influence field on opportunities allows you to track which campaigns are produce opportunities. This needs to be enabled.
The campaigns hierarchies feature allows you to create parent/child campaign relationships. Can only have one parent but unlimited children. Maximum of five levels. Access this by clicking view hierarchy on the detail page.