A lead is a CRM object containing information (telephone number, email, website) of a person or company who has the potential to become a customer – that is, to complete a deal. A lead is the beginning of the process, thus the information contained in a lead may come from a business card collected at a conference, the company website, or a phone call coming in to the sales department.
Leads can be assigned various statuses which determine how the lead will progress through the CRM. At some point, a lead will either be removed from the system (junk) or converted to a Contact, Company, or Deal.
Leads can be added automatically using data from forms on your web site.
If your website is based on Bitrix Site Manager, setting up integration with the CRM is done in the Web Forms module. Otherwise, you can transfer data to the CRM using the Rest API, which is also simple to set up.
More details about lead creation from web forms can be found here.
More details about using the Rest API can be found here.