Deals are sales opportunities you strike with your customers. You can create deals,
From the Quick actions bar
While viewing an account or a contact's details page.
To create a deal,
Go to the Add Deal overlay using anyone of the ways listed above.
Enter the deal details under Basic Information and Additional Information (if any).
Click Save once you’re done.
You can find the created deal in the Deals list view page. The deal can also be found in the details page of the contacts associated with the deal. And also on the details page of the account to which the deal belongs.
Here’s the list of default fields in the web application. You can always create custom fields to capture additional information for the deals.