Interest explained

 All but the most basic of current accounts provide interest on credit. However understanding the rate can be confusing because of the number of different terms used. The most frequently used terms have been listed below with definitions alongside them. As a quick reference, there are basically two kinds of interest; the type you pay on your overdraft, credit cards or loans, and the type the bank your building society pays you, on savings. The reason for the number of different terms is due to additional charges like taxes, administration costs etc which alter the total amount.
AER
The most commonly displayed representation of interest rates on savings. It stands for Annual Equivalent Rate and is the amount of interest you can expect to receive on your savings at the end of one year.
Gross
Like the AER, this is another representation of the interest you will get on savings. It shows the interest payable before the deduction of income tax*.
Net 
Similar again to AER, except this time the income tax* has been deducted, so you see a more realistic representation of how much interest you will get after one year.
Tax Free Rate
If you are exempt from paying income tax*, such as students, then this is the rate which applies to you. It shows you the annual interest rate.
EAR
This stands for Equivalent Annual rate and shows how much interest you have to pay on your overdraft every year if you don’t take into consideration additional charges like administration and banking fees.
APR
This stands for Annual Percentage Rate and is similar to the EAR in that it is a representation of the amount of interest that you have to pay on your overdraft. What distinguishes it from the EAR is that it does take into consideration additional charges, like administration, arrangement, security and banking fees. When these factors have been taken into account, the consumer has a more accurate view of how much they will have to pay each year.
Summary
For basic current accounts with few features, there is usually a lower rate of interest on credit, while on larger accounts the rates are generally more competitive. Rates are often relative to your balance, with the more credit you have in them allowing you to earn more interest. But the same can often be said for debit: the more overdrawn you are, the more interest you pay.
Lastly, while the terms APR and AER give a good idea of how much money you can save or will have to pay out, be aware that they are dependent upon the overall economic state in the UK, and so can vary.
*Interest rate is the rate which is specified by the law