Financial		Logical		Informational		Text
Mathematical		Statistical		Lookup		Reference		Formula Errors

All Formulas start with " = " ( Equal to Symbol)

Alternatively you can also begin with ' + ' or ' - ' and start the Formulas.
Excel recognizes and converts the ' + 'and ' - ' to ' = 'Symbol when you hit enter
You may review the Cell Formula after you Hit enter to understand better

The formula conversion does not happen when you use ' / ' or ' * ' arithmetic operators

You may alternative select a cell and Choose Fx from the Function tab to write formulas

Optional components in a formula are displayed within [] brackets
Eg:SUM( number1, [number 2], ... [number n] )

Formula and Results switching
Formulas ->Show Formulas - Switch between Formula and Results view

  CTRL+`

Evaluate formula
Formulas -> Evaluate Formula - View how the formula is evaluated step by step