CampaignAn organized email outreach effort targeting a group of contacts. Campaigns can include multiple emails, A/B testing, scheduling, and detailed analytics for open rates, click rates, and conversions.ContactA person record in the CRM, typically associated with a company. Contacts store personal details, communication history, and activity timelines.Contact GroupA saved list of contacts used for bulk operations such as campaigns, exports, or targeted outreach. Groups can be static (manually curated) or dynamic (automatically updated based on filter criteria).Custom FieldA user-defined data field added to entities (companies, people, opportunities) beyond the default system fields. Custom fields support text, number, date, dropdown, and other types.