Writing instructions for bead weaving patterns is complicated, as anyone who has done this knows. Bead weaving doesn't have as many standard terms as, say, in knitting. There's isn't always a "top" or "bottom" to a piece, and depending on how someone holds their work the direction they're going may be very different from what the instructor intended. So understanding a few standard phrases can be just the ticket to get you from "huh?" to "got it!"
Let's start with Pass Through or Pass Through Again. It's simple enough, really. It means you'll bring your needle through the bead or beads again in the same direction as before. This diagram shows how the thread has looped around these beads to go through them a second time in the same direction. It's a phrase that always seems to make perfect sense until you see another, similar phrase, that gets you confused.
Pass Back Through is that above mentioned "confusor" phrase. (I know -- confusor is not a real word -- I just made it up.) Pass Back Through means you'll bring the needle back through the beads you just exited, in the opposite direction. This usually means you'll skip one or more beads to act as anchors holding everything in place. So the instructions will probably say something like "skipping the last three beads, pass back through the beads just strung."
Now you're ready to practice your new language skills. Go find a bead weaving pattern and give it a whirl -- you might surprise yourself and have something to show for it!