The kick beat is each individual kick within your stroke cycle, which is one stroke with each arm, i.e. one right arm and one left arm. Typical rhythms of stroke tend to be two-beat, four-beat, six-beat and, in extreme cases, eight-beat. As a general rule, the shorter the distance and the harder the effort the more kicks you’re likely to do to every stroke.
Traditionally, tri coaches will recommend to kick less in the swim (a two- or a four-beat kick) to conserve energy. But studies have shown that kicking doesn’t actually use more energy to swim at the same speed or quicker, though this does rely on an efficient kick and good body position. So this means keeping an extended, straightish spine and neutral head and neck position to keep the hips as high in the water as possible, paired with a kick from the hips and your legs staying reasonably straight.
Play around with how much your legs kick within your stroke. Everyone will have their own natural rhythm, just make sure whatever kick you do is purposeful.