The countif function in excel count cell value by given criteria and sumif function sum the values of cell by mentioned criteria as shown below
How to use Countif and Sumif in Excel:
As shown in below image you can see how to use countif in excel and how to use sumif in excel.
If in a column you want to count how many values are greater than or less than particular values you can use countif as shown below. Below example show how many persons salary are less than 10000.