Pacing is when you enter the other person model of the world on their terms. Like walking beside them at their pace. Once you have paced another person, established rapport and shown that you understand where they are coming from then you can lead them.
Leading is when you use the influence that you have built up from pacing. When you scratch your nose they go on to scratch theirs.
Pacing and Leading are NLP techniques associated with Building Rapport which is a process that we train at our NLP Training courses and this training is available to you online in our NLP e-Learning centre.