Standard Objects with Definitions

Campaigns:

A campaign is any marketing project that we want to plan, manage and track in salesforce.Represents and tracks a marketing campaign, such as a direct mail promotion, webinar,or trade show.

Leads:
A lead is any person, Organization or company that may be interested in our products.Sometimes leads are referred to as prospects or suspects leads are not yet customers.

Accounts:

An account is an organization, individual or company involved with business such as customers, competitors and partners that wish to track in salesforce.

Contacts:
A contact is any individual or influence associated with an account that we want to track in salesforce.

Opportunity:
An opportunity is any potential revenue generated event (Sales deal) that we want track in salesforce.

Cases:
A customer issue such as a customer’s feedback, problem, or question.

Solutions:
A detailed description of a customer issue and the resolution of that issue.

Forecasts:
A forecast is best estimate of how much we generate in a quarter.

Reports: 
Reports are summaries and analyses of data which we can display or print.

Dashboards:

Dashboard give us a real time snapshot corporate metrics and key performance indicates. A dashboard is a group of different charts that graphically display custom report data.

Task and Events:

• Activities is the term for both Tasks and Events. There is no "Activities" object, there is a"Task" and "Event" object in the API. You can think of Tasks and Events as "Types of Activities".
• In the UI these records for both objects show up in the "Open Activities" and "Activity History" related lists. Tasks and Events are special standard objects in Salesforce.com.

Documents:
A file that a user has uploaded. Unlike Attachment objects, Documents are not attached to a parent object.