Salesforce Web-to-Lead is the default way to import Leads into Salesforce from a web form. The way it works is simple: you select the fields to include in your form and Salesforce generates HTML code, which can be embedded in your website. When the form is submitted, an API request is sent to your instance and a lead is created. Once the lead is created, lead auto-response and lead assignment rules are fired to determine the next actions.
Learn more about building and customizing Salesforce Web-to-Lead forms in our latest article on forcetalks.