Nearly all Droids are programmed to understand a binary computer language used by most computers and intelligent machines. The simple version of this is a language skill called Binary. With it, Droids can communicate with computers and each other. Binary allows a computer or droid to communicate mathematical or technical information in great detail at a very high rate (Approximately 100 times as fast as normal speech), but it has great difficulty expressing nontechnical topics such as emotion, art philosophy, or The Force. For example, as a Free Action, a Droid can use Binary to describe the exact location and physical description of all objects and characters that the Droid detects in a 10-by-10-square area, but the Droid would be unable to express the nuance of a conversation or the emotion conveyed by body language.
Obviously, some Droids can understand additional languages as well- most Droids in the galaxy are programmed with Basic, even if they can't actually articulate the language. Some living beings learn to intercept the Binary language of the Droids, even if they can't themselves speak an approximation of it. A living being who understands Binary cannot understand the same volume of information as another Droid or computer, so the speaking Droid must voluntarily slow it's speech to normal rates (That is, the same as Basic or any other language) so that the living being can understand it.