question on using for

[tryingtolearnpython]

trials = 10000
successes = 0

for _ in np.arange(trials):
    rolls = np.random.choice(dice, k)
    if sum(rolls == 6) > 0:
        successes = successes + 1

successes / trials

in the code above, what does it mean to use _ after for?

for _ in np.arange(trials):