The Inquiry Element is a unique feature of the Denali that does not appear in WP-Property. It takes the native WordPress comments system and changes it to an inquiry form so site visitors will be able to contact you directly about a particular property. On the settings UI tab you get the following options:
Don't treat property comments as inquiries: If you check this, the Inquiry system will be disabled and normal WordPress comments will appear underneath your properties. Not suggested.
WP-CRM Inquiry Forms: If you have WP-CRM installed and enabled on your website, you will be able to create forms with custom fields for the visitors' Inquiries. For each property type you can choose a different form. Of course, you can imagine how powerful a feature this is for your business, since you can customize the information your leads will send you and filter people by them. So you'd better download and use WP-CRM, it's an amazing lead-generation plugin. Oh, and it's a CRM too.
If not, you can always use the next settings section to keep the same form for all property types.
Default Form Fields: Here you can set the fields for the default forms. Useful if you don't have lead filtering needs and you just want to keep things simple. In this UI you can add (and remove) rows of form fields for the information you want to keep (by clicking the "Add Row" button). You can also set fields as required. Each row represents a single field. If you don't know what the slug is, don't worry about it.
And if you click on "Show agent dropdown on inquiry form listing all agents associated with the property" your visitor will be able to choose an associated agent and the sent email will be directed to him.