Counta()

This formula helps to count only cell with values in the given range. It will exclude blank cells.

=Counta(range)

Range= Area/ Range to count

Count()

This formula will only count cells containing numbers in the given range.

Count( Range)

Range = Area where count is to be performed

Countif()

This formula will help you to Count according to condition.

=Countif(range, criteria)

Range= Area for which count is to be performed.

Criteria= What is required to count.

For ex: There is a messed data of sales.
You want total count of a particular deal. This is where you can use this formula.

Vlookup()

This formula helps to pull required data from entire data.

For example: In sales data if I want to pull  
Salesperson Name for specific deals vlookup can be used.

=Vlookup(lookupvalue, tablerange,col index,range lookup)

Lookup Value= In above example Lookup value is deal number.
Table range= Range will start from column with deal details and end with column with salespersons detail.
Col index= Column number of salesperson column in your range.
Range lookup= Keep always "0". This means exactly same

Sumif()

This formula helps you to sumup only those cell which you require based on near by column.

For ex: There is a messed data of sales.
You want total sales by sale agent xyz. This is where you can use this formula.

Formula:

Sumif(range, criteria, sumrange)

Where.
Range= Criteria Range. In the above example range containing agents name will be the criteria.

Criteria= Criteria or Condition. In the above example cell containing agents name for whom you want total sales(freeze it) or you can type the name manually in double quotes.

Sumrange= The range which you want to sumup. In the above example range containing sales numbers.

Mid()

=mid(text,start no,num char)

This formula is like left and right formula
but it pick the no. of digits you define from/after the digit number you tell.

Text= Cell number
Start no= From left from which digit you what to start.
num cha= Number of Characters from the start no.

Networkdays()

=Networkdays(Start date,End date,Number of holidays in a week)

This Formula will help to get number of working days for a defined period.