ok, well, there is a lot you can learn here about boolean equations, but I'll just do the simple stuff for ya

&& means 'and',

|| means 'or'.

> greater than

>= greater or equal to

< less than

<= less than or equal to

!= not equal to

with boolean operations, you can also use brackets to make it more readable and help with grouping equations (which is very helpful when learning - I'll use excessive brackets so it's more clear what's happening)

basically, the if statement needs a (boolean) "true" value to execute.

so;

ActionScript Code:

if ( true )
{
trace("this will execute every time");
}
if ( false )
{
trace("this will never execute, ever");
}

so, we just basically work out our boolean equation and shrink it until it's either true or false, we'll start by taking an overly complicated if statement and working it out and shrinking it to see what happens;

if ( ( (10 > 5) && (10 > 50) ) || ( ( 100 > 5000) || (100 == 100) ) )

if ( (true && false) || (false || true) )

if ( (true && false ) || true )

if ( false || true )

if ( true )

so,

true or true == true

true or false == true

true and true == true

true and false == false

ActionScript Code:

var myNumber:int = 22;
var yourNumber:int = 33;
var otherNumber:int = 55;
var negNumber:int = -44;
if ( (myNumber < yourNumber) && (myNumber > 0) )
{
trace("yourNumber is greater than myNumber and myNumber is greater than 0");
}
//remember, || this means 'or'
//so,
/*
if ( ( 22 > 33 ) or ( 22 > 55 ) or ( 22 > -44 ) )
if ( ( false ) or ( false ) or ( true ) ) */
if ( (myNumber > yourNumber) || (myNumber > otherNumber) || (myNumber > negNumber) )
{
trace("myNumber is greater than at least one of the other numbers");
}
/*you can also mix them up
if ( ( 22 > 33 ) or ( ( 22 < 33 ) && ( 22 > 0) ) )
if ( ( false ) or ( ( true ) && ( true ) ) )
if ( ( false ) or ( true ) ) */
if ( (myNumber > yourNumber) || ( (myNumber < yourNumber) && (myNumber > 0) ) )
{
trace("true");
}

Hopefully this is enough to get you started. This is just the surface of boolean algebra, I'll leave the more advanced stuff out. You can look into that when you're more experienced