{...} (block)

Blocks are one or more statements enclosed in braces. Typically used with function definitions and control flow statements.

{
    Statements
}

Remarks

A block is used to bind two or more statements together. It can also be used to change which If statement an Else statement belongs to, as in this example where the block forces the Else statement to belong to the first If statement rather than the second:

if (Var1 = 1)
{
    if (Var2 = "abc")
        Sleep, 1
}
else
    return

Although blocks can be used anywhere, currently they are only meaningful when used with function definitions, If statements, Else, Loop statements, Try, Catch or Finally.

If any of the control flow statements mentioned above has only a single statement, that statement need not be enclosed in a block (this does not work for function definitions). However, there may be cases where doing so enhances the readability or maintainability of the script.

A block may be empty (contain zero statements), which may be useful in cases where you want to comment out the contents of the block without removing the block itself.

One True Brace (OTB, K&R style): The OTB style may optionally be used in the following places: function definitions, If (expression), Else, Loop Count, While, For, Try, Catch, and Finally. This style puts the block's opening brace on the same line as the block's controlling statement rather than underneath on a line by itself. For example:

MyFunction(x, y) {
    ...
}
if (x < y) {
    ...
} else {
    ...
}
Loop %RepeatCount% {
    ...
}
While x < y {
    ...
}
For k, v in obj {
    ...
}
Try {
    ...
} Catch e {
    ...
} Finally {
    ....
}

Similarly, a statement may exist to the right of a brace (except the open-brace of the One True Brace style). For example:

if (x = 1)
{ MsgBox This line appears to the right of an opening brace. It executes whenever the IF-statement is true.
    MsgBox This is the next line.
} MsgBox This line appears to the right of a closing brace. It executes unconditionally.

Related

Function Definitions, Control Flow Statements, If Statements, Else, Loop Statements, Try, Catch, Finally

Example

if (x = 1)
{
    MsgBox, test1
    Sleep, 5
}
else
    MsgBox, test2