Tbl--exactly that. Normally you put your needle through the front loop, right? When you knit tbl, you put your needle in the leg of the loop that comes down the back of the left needle. No biggie.
Three needle bind off is done with three regular needles.
It's most commonly used at a shoulder seam but is also used on the infamous clogs.
You are basically knitting the front and back of the shoulder together and binding them off at the same time. It makes the most wonderful seam you can imagine!!