Apex Trigger and Flow are both tools used in Salesforce for automation, but they have different use cases and functionality.

Apex Trigger:-

1. Apex Trigger is a Salesforce feature that allows developers to write custom code in Salesforce to automate business processes.

2. Apex Triggers are executed when specific events occur, such as when a record is created, updated, or deleted. 

3. Developers can write custom logic in Apex Trigger to perform actions such as updating records, sending emails, or creating new records.

4. Apex Triggers are generally used for complex business processes that require custom logic.

5. They provide developers with the flexibility to create custom automation that cannot be achieved with standard Salesforce automation tools.

Flow:-

1. Flow is a visual workflow automation tool that allows Salesforce administrators to automate business processes without writing code.

2. Flows can be used to automate processes such as updating records, creating new records, sending emails, and more.

3. Flows are created using a drag-and-drop interface that does not require any coding knowledge.

4. Flows are generally used for simple to medium complexity business processes that can be automated using standard Salesforce automation tools. 

5. They are a great alternative to Apex Trigger for administrators who are not familiar with coding.

In summary, Apex Trigger is a tool for developers to write custom code for complex business processes, while Flow is a tool for administrators to automate business processes without writing code.