To reduce hum caused by poor electrical grounding, one often has to ground the turntable, as well as the tonearm, usually to the phono stage chassis ground lug. So that’s electrical ground, and that can cause hum if ground is poor, or if the two ground planes are at different voltage levels with respect to zero voltage. to reduce ticks and pops caused by static electricity, one often also has to ground the turntable. The solution is the same, but the problems are different in origin. Ticks and pops and static arcs jumping across to your finger as you touch the tonearm are caused by static electric charge build up. That happens for many reasons, but in my opinion, the most common cause is us. When we walk up to the turntable, we often build up a static charge on our bodies, which is immediately transferred to the LP. Furthermore, the act of removing an LP from a sleeve will in itself cause a charge to build up on the LP surface. There are many other aspects to this, and there are a few other threads about this with some good and some bad information.