Lead nurturing is an advanced form of marketing and is often used as part of a marketing automation programme. Ultimately, you nurture leads down the marketing funnel, in order to move leads from the top of the funnel through to the bottom of the funnel.
A lead continues to be nurtured by presenting marketing content which is geared towards their current state, i.e. if the lead is at the top of the funnel they would get problem statement exploratory marketing, however if the lead was at the bottom of the funnel they would be nurtured towards qualifying as an MQL by being presented with solution driven marketing content, featuring the product or service offered as a needs payoff.