Permission sets are used to grant additional permissions and access settings to individual users without changing their profiles or requiring a new profile to be created. You can use permission sets to extend users' functional access without changing their existing profiles. To meet the request of giving comprehensive edit access on Campaigns to a few marketing users who have read-only access by default, you need to create a permission set with edit access onCampaigns and assign it to those users.References:https://help.salesforce.
com/s/articleView?id=sf.perm_sets_overview.htm&type=5