➢ A statement is a directive that tells the computer to do something. A Boolean expression is an expression that is either true or false. In Scratch, any block shaped like an elongated diamond is a Boolean expression.
➢ A condition is thus said to "evaluate to true" or "evaluate to false." In Scratch, any block whose label says "if," "when," or "until" is a sort of conditional construct. A loop can induce multiple executions of statements. In Scratch, any block whose label begins with «forever» or «repeat» is a looping construct.
➢ A variable is a placeholder for some value, much like x and y are popular variables in algebra. In Scratch, variables are represented with blocks shaped like elongated circles, uniquely labelled by you. Variables, generally speaking, can be local or global. In Scratch, a local variable can be used by just one sprite; a global variable can be used by all of your sprites.
➢ An event, then, is like a message from one thread to another. In Scratch, blocks whose labels begin with "broadcast" signal events whereas blocks whose labels begin with "when" handle events effectively represent threads themselves.
➢ Scratch has 5 conditional and looping statements: