The World Anchor is a block that keeps the chunk it is in loaded when no one is nearby.
The area loaded is 3x3 chunks (for a total of 9 chunks) centered on the world anchor ([http:// source]).
A chunk is a 16x16 block area. () While a World Anchor is placed, devices such as Furnaces, Energy Collectors, etc. will continue to work as if you were standing beside them. The Anchor Cart is the minecart version.
Pressing F12 will cause an aura of purple particles to show which chunks are being affected by a World Anchor or Anchor Cart.
This may not work in servers because particles are client side and not server side.
Excessive use of World Anchors can cause lag. Sparing use is advised.