Azure Dashboard is an organized view of your resources. So you can add your resources to azure dashboard and your resources in it. This allows a quicker way of locating your resources. Also you can create the dashboard and share it. You may create different dashboards for different teams so that each team will have quick access to the resources that is relevant to them.
Azure Monitor, in another hand is a monitoring solution that allows you to collect, analyze and take action on both your Cloud and On-Premise workloads. It collect logs and metrics. It collect data such as
Application Monitoring Data
OS Monitoring Data
Resource Monitoring Data
Subscription Monitoring Data
Tenant Monitoring Data
Refer: https://learn.microsoft.com/en-us/azure/azure-monitor/overview
Hope this helps