Attribution is all about assigning credit to advertising efforts on multiple platforms. Attribution models are rules that determine how credit for sales and conversions are assigned to touchpoints in the conversion path. Last$-$click attribution gives credit for a customer's action to

$40\%$ credit is assigned to each the first and last interaction, and the remaining $20\%$ credit is distributed evenly to the middle interactions

the most recent source that brought the individual to the point of action

the first source that can be tracked by web analytics

only sources that have been coded with web analytics