A lead is a data set containing the contact information of an interested party who voluntarily makes this information available to a company in the context of marketing. A lead consists of the name of the prospective customer, and contact details such as address, email address, telephone or fax number.
By providing their user data, the potential customer expresses a need which the company can then use for further marketing campaigns to make the potential customer sales ready. The costs for generating a lead in the lead generation process are referred to as cost per lead, and this varies depending on the quality of the data set.
Leads are usually scored so that they can be differentiated in terms of their quality. This simplifies access to the data records and helps to structure the methods of lead generation. Full leads with all the necessary information can be used for sales, but this is not the case for incomplete data sets. 
An important step in lead generation is the labelling and processing of the data so that it can be structured and its accuracy checked. Differences between the B2C and B2B areas can occur. Leads can be categorized into five quality levels. 
The definition of a lead has an impact on the lead generation process. It forms the basis for subsequent campaigns. The methods of lead generation differ in that the lead can contain different characteristics. A postal address can only be used for offline leads, while email addresses can be used for different online leads. All persons involved in this process should agree on the definition so that it is clear what the company wants to achieve. All collected leads should be reviewed and evaluated with regard to this definition.
When determining the characteristics of a lead, it is important to determine which strategic goals are pursued and what is an ideal lead for the company. Increasing reach by collecting a high quantity of leads is a fundamentally different goal than increasing sales through high-quality leads that are already "sales-ready". The goal is usually to create sales-ready leads. Lead nurturing is therefore an important step in the creation of leads.