It looks to me like two rows of beads but tied on one piece of thread in a loop. The black thread weaving in and out looks like a different piece entirely, but it's possible it is the same thread continued. Either way it was weaved seperately to the beads. The two ends of the strings would then go through the large silver bead acting like a slip knot, allowing you to enlarge and shorten the length of the bracelet as required.
The way I'd make it initially would be to thread a load of beads on one piece of string and tie then string in a loop, but leave enough space between the beads to allow for the black weaving thread. Then pull either end of the loop so that an equal number of beads face each other on the horizontal and leave extra thread at the knot end. At this point I'd tie an extra piece of thread to the open end of the loop .Then I'd fix these to a wooden board with clips to make the weaving process easier. Then weave in and out with a new piece of thread, tying and cutting then ends.
The two ends of the loop can then be passed through a larger bead to make the slip knot, but make sure the hole in the bead is small enough to provide friction, which is what stops the braclet undoing itself. Alternatively you could simply tie it onto your wrist, or add a large bead on one side and a loop on the other, or even tie on a jewelry clasp.
There'll be many ways of making it, the above is only one way. Hope it makes sense