Total profit means the total revenue excluding the total cost of the certain products.
Average profit defines the profit which comes and achieved after selling each unit. Total revenue/quantity is average profit.
Marginal profit defines the extra profit which an organization achieves.
Marginal profit is change in total revenue/change in quantity.
Incrementalism defines the doings and aim which takes little time but it is done in small small steps.
Marginalism defines the additional usage and extra benefit which one has achieved from his incremental changes. It is a very powerful technique to deal with the problems.