401K -> Traditional IRA -> ROTH IRA

How do these transfers work, & when do I pay taxes?

Most importantly, is this what is commonly referred to as a "Backdoor Roth IRA"?

Starting next year I am likely to slip into a limited Roth IRA Contribution limit due to salary increase.

How can I use 401K or Traditional IRA to still make contributions to my existing ROTH IRA?