By default we have system fields for various entities present in neetoCRM. For leads we have fields such as contact name, company name, lead name, contact email, contact phone and owner.
If you want to add more fields on leads such as state, city, country etc then you can add this fields as custom fields on lead.
Go to Settings->
Custom fieldshere you can add, delete, update custom fields for lead. This lead custom fields would be then present in lead form, lead show page, lead list page.
Similarly you can add custom fields for contacts, deals, companies, products.