The simplest expression is a single literal data value; for example,

6 // The number 6

"eloign" // The string "eloign"

You can use operators to join multiple literals; for example,

6 + 456 * 3 // The number 1374

"sep" + "a" + "rat" + "e" // The string "separate"

To see the value of an expression in the Command window, precede the expression with the ? symbol:

? 6 + 456 * 3 // Displays 1374