Definition for Workflow or Workflow Manager
Workflow is a function to do the business work in step by step fashion. Workflow make your business work easier.
Workflow is very important in SharePoint.
In SharePoint there are 2 types of workflow.
Sequential workflow and State Machine Workflow.
Sequential Workflow: This is very simple workflow. The next step in Sequential Workflow is predictable. You can say it is straight forward workflow. Take the example of a application approval process in a office. In this process one person will send the approval email, and it will be forwarded to higher authority person.
Then here two conditions can be generated. Either application will be approve or it will reject. So, any one can predict the next step of this process. In this type of situation you must use Sequential Workflow.
State Machine Workflow:
This workflow is quite complex. In this type of workflow no one can predict the next job. Means you can say that there will be various paths in this type of workflow. In State Machine Workflow there is a possibility of backward direction.