SharePoint Designer can be used to create powerful workflows on owr sharepoint site.we can create workflows on a list or library, create reusable workflows or create site based workflows. While  create a list workflow in sharepoint designer, will get various capabilities of the workflow designer environment (such as steps, conditions, actions, parallel branching, moving actions around etc). After adding item into the sharepoint list send the mail to assigned user using sharepoint designer. Go to the sharepoint designer ,select the workflows option  and then select the list workflow, Here we have to select the our custom list.then after give the workflow name and description Here we have option to design our workflow, am selecting the Send an Email Here click on these users button, then one popup will open to select the user. Here select the actions  name called go to end workflow Here we can find the task list and workflow will start manually or automatically options. After selecting the options click on save and publish button Go to the sharepoint site  add the item into the list and check the workflow  status.