R in a Nutshell, 2nd Edition

Symbols

Formally, variable names in R are called symbols. When you assign an object to a variable name, you are actually assigning the object to a symbol in the current environment. (Somewhat tautologically, an environment is defined as the set of symbols that are defined in a certain context.) For example, the statement:

> x <- 1

assigns the symbol “x” to the object “1” in the current environment. For a more complete discussion of symbols and environments, see Chapter 8.