Difference between reference/recommendation What is exactly the difference between a reference letter and a recommendation letter in Academia? According to Wikipedia: 


  Letters of recommendation are very specific in nature and normally requested/required and are always addressed to an individual, whereas letters of reference are more general in nature and are usually addressed "To Whom It May Concern".


However, I've often seen applications where it was asked to provide letters, without being explicit about whether it should be recommendation or reference letters (according to the previous definition). 

I only ask letters from persons with whom I have worked closely (typically my former advisors), because I believe they are the best persons to ask about me, but it seems that some people also include letters from persons they just know. 

In other words, what exactly is expected when a job application asks to "give references who can provide recommendation letters"?
With due deference to Wikipedia, colloquially, the two terms are used interchangeably.