What are the different access rules?

For block dependencies, the default and only option is Show, where we show the block.
For field dependencies, you can choose among the following options:

• Show (Read + Write) - Show the field with a read and write access.
• Show (Read + Write & Mandatory) - Show the field and make it mandatory with read and write access.
• Mandatory - Make the field mandatory.
• Show (Read only) - Show the field with only read access.

Fields that are defined as mandatory at the module level (in Detail View Layout) are not affected by the access rules set in Dependent Fields and Blocks. This applies only to Show (Read + Write & Mandatory) and Mandatory access rules.
To know more about Dependent Fields and Blocks, click here.