A formula is an expression that can perform calculations, manipulate and return information.
Formulas are used for calculated values inside a document or across multiple documents.
Formula field
![Formula](/img/help/formula-join.png)
The Formula field is a special field that evaluates a formula.
Summary
![Sum field](/img/help/formula-sum-field.png)
The Summary feature allows you to perform calculation across multiple documents, for example the sum of a field.