A first click model is a conversion attribution model which give all credit for conversion to the first touch point or digital marketing channel to which is exposed a consumer.
Usually, only channels with which the consumer really interacts are taken into account for first click attribution.
The model is equivalent to last click model for impulse buying because the first click is also the last click before the conversion.
Notwithstanding its limitations, the first click model may sometimes make sense for unknown brands or products when the offer is really discovered thanks to the first channel.
The model is also called first interaction model.
See other attribution models.