AER means "Annual Equivalent Rate" and is the interest rate you would earn in a 12-month period if you put your money in an account at the beginning and left it there for a full 12 months without adding to it or taking away from it, other than the interest you receive.
APR means "Annual Percentage Rate" is designed to be a clear comparison tool between products. It includes all interest and any fees, so is the net effect of the product on your wealth.
Interest rate 'blending' is the term given to placing different sums in different accounts on different rates of interest to arrive at an overall, or 'blended' interest rate on the funds.
Compounding in interest is the effect of having a sum of money which earns interest over a period. Over the following period, the interest is earned on the original sum and the amount of interest earned so far.
Liquidity in investment terms simply means 'how quickly you can turn your investments into cash'.