"R is an open source programming language and software environment for statistical computing and graphics that is supported by the R Foundation for Statistical Computing.

The R language is widely used among statisticians and data miners for developing statistical software and data analysis.""

• a programming language
• a statistical package
• open source

• a database
• a spreadsheet
• commercially supported

• It's free
• It's powerful
• It's popular

Source: Revolution Analytics

It can be frustrating.