Fixed Cost

Fixed costs are the costs which do not change with change in the level of output. Fixed cost is defined as the expenditure, on hiring or purchasing of fixed factors/inputs, which are compulsory and has nothing to do with the amount of production of the good or service.
For example: Suppose you start your own production business by taking a loan from bank and hiring an office building.Even If you do not start production, you will have to pay rent of office building and interest on loan. Hence rent of officebuilding and interest on loan here is fixed cost.

Variable Cost

Variable costs are the costs that directly vary with changes in the level of output. We can define variable cost as the expenditure on variable factors/inputs, such as labour, raw material which can be changed.

Break even point*

Is the point at which cost and revenue is equal i.e. there is no loss or profit.Sales above the BEP will generate profit to the firm. Sales below BEP will lead to loss to the firm.

Shut down point*
When firm is incurring losses but can cover its variable cost from its revenue then it should continue the production as fixed cost will always be incurred whether to continue the production or not.
When revenue cannot even cover the variable costs of production then at this point firm should shut down the production.
Marginal cost *
Marginal cost means extra/additional cost incurred on additional unit of production.It is dependent on the variable cost only as fixed cost remains constant on every additional production.
 

Marginal Product (MP)

MP is the addition to the output resulted due to addition of one extra unit of input.

Law of diminishing marginal product*

It says that if we keep on increasing the input (e.g. labour or raw material), with other inputs fixed, marginal product will increase initially till certain point is reached after which the resulting addition to output (i.e., marginal product of that  input) will start falling.
For example- One labour is producing 80 units of a product in a 8 hour working day (i.e. 10 unit per hour) If he works overtime for another 8 hour then initially he may produce 10 unit per hour for 2 or 3 hour after which his production will fall due to overworking.

Marginal Utility

Marginal utility is the addition to the total utility derived from the consumption of an additional unit of a commodity 

Law of diminishing marginal utility*

When we get more and more units of a commodity, the intensity of our desire for that commodity tends to diminish. The law of diminishing marginal utility also explains the same thing. It states that ‘as more and more units of a commodity
are consumed, marginal utility derived from each successive unit goes on diminishing.’Suppose, a thirsty man drinks water. The first glass of water he drinks will give him maximum satisfaction (utility). Second glass of water will also fetch him utility but not as much as the first one because a part of his thirst is satisfied by drinking the first glass of water. It is just possible that he may get zero utility from the third glass because his thirst has now been satisfied.
There will be negative utility from the fourth glass of water. Any rational consumer will not consume additional glass of water when it gives disutility or negative utility.