The term Object is used in multiple places in Bedrock Data. An object is a component of your software platform where data lives. A similar term for Object is Module.
Types of objects will vary from system to system as well as what they are called by each system. Common objects are Lead, Contact, company and opportunity. All of the data related to an individual will tend to live under the lead and contact objects. For example, first name, last, email, phone number, etc. While all of the information about a place of business will live on the company object and all of the information about a current sale will live on the opportunity object.
Other objects you may use are Account, Deal, Registrants, Event and Attendees for event-based systems.
On the account object, you will see data like the number of employees, account name, billing account, industry, etc. On the opportunity object, you will see data like close date, stage, revenue. For event-based systems, you will see fields like event date, registration type and date, event status, etc.