Types of Organizations
Production Organizations is the one where client organization works in real time. It contains original data and actual code deployed. Users can log into the production Org at https://login.salesforce.com. All usernames must be unique across all production Orgs.
You can create multiple copies of your production org for development, configuration, testing or training without affecting your production configuration and data.
Users can log into sandbox Organizations at https://test.salesforce.com.
A developer Organization is a free, non-expiring copy of an Enterprise Edition environment that you can use to instantly start developing, testing and deploying your applications.
To sign up for Developer Organization user can log on to http://developer.force.com to get free developer edition link.
Partner Developer Organization
Partner Developer organization is a free Developer Org with more storage, features and licenses for companies who are enrolled in the partner program.
Types of Sandboxes
A Developer sandbox is intended for development and testing in an isolated environment. A Developer Sandbox includes a copy of your production org’s configuration (metadata).
Developer Pro Sandbox
A Developer Pro sandbox is intended for development and testing in an isolated environment and can host larger data sets than a Developer sandbox. A Developer Pro sandbox includes a copy of your production org’s configuration (metadata).
Partial Copy Sandbox
A Partial Copy sandbox is intended to be used as a testing environment. This environment includes a copy of your production org’s configuration (metadata) and a sample of your production org’s data as defined by a sandbox template.
A Full sandbox is intended to be used as a testing environment. Only Full sandboxes support performance testing, load testing, and staging. Full sandboxes are a replica of your production org, including all data, such as object records and attachments, and metadata.
Creating Salesforce Account
Creating a developer edition salesforce account.
Go to http://developer.force.com
Salesforce Career Path and Certifications
Salesforce Advanced Administrator
Salesforce Certified CPQ Specialist
Salesforce Certified Platform Application Builder
Salesforce Certified Platform Developer I
Salesforce Certified Platform Developer II
Salesforce Certified B2C Commerce Developer
Salesforce Certified Marketing Cloud Developer
Salesforce Architect Certifications:
Certified Data Architecture and Management Designer
Certified Sharing and Visibility Designer
Certified Development Lifecycle and Deployment Designer
Certified Identity and Access Management Designer
Certified Integration Architecture Designer
Certified Mobile Solutions Architecture Designer
Salesforce consultant certifications:
Salesforce Certified Community Cloud Consultant
Salesforce Certified Sales Cloud Consultant
Salesforce Certified Service Cloud Consultant
Please check below video for more detailed explaination: