If else

If/else is the basic flow control statement. Let's look at this sentence:

If it's raining I'll take an umbrella.

Using an if statement, that sentence would be written like this:

if(bRaining)
{
    bUmbrella = true;
}

We could also add an else statement to it:

If it's raining I'll take an umbrella, otherwise I'll wear short sleeves.

That would be written like this:

if(bRaining)
{
    bUmbrella = true;
}
else
{
    bShortSleeves = true;
}

We can also use Else If for other conditions.

If it's raining I'll take an umbrella, or if it's cold I'll wear a coat, otherwise I'll wear short sleeves.

We could write that like this:

if(bRaining)
{
    bUmbrella = true;
}
else if(Temperature < ComfortableTemperature)
{
    bCoat = true;
}
else
{
    bShortSleeves = true;
}

The important thing to remember about else/if is, that only one of these conditions will run. If it's raining and cold, only the bRaining section of the code will run, not bRaining and Temperature < ComfortableTemperature.