Physics, or sorcery?

Why? The weight of the buckets holds them against the table/the table against them.

Basically, you have three forces acting on the buckets:

  1. Gravity, in proportion to the weight of the buckets, pulling them down.

  2. Tension from the rope, in proportion to the weight of the table, pulling them up.

  3. Normal force, or the fact that two solid objects can’t pass through each other.

And three forces acting on the table:

  1. Gravity, in proportion to the weight of the table, pulling it down.

  2. Tension from the rope, in proportion to the weight of the buckets, pulling it up.

  3. Normal force, or the fact that two solid objects can’t pass through each other.