I'll assume everyone knows what Litematica is: a mod which loads in a 'hologram' image of a saved schematic, allowing you to easily place all the blocks in the right places.
Essentially - easyplacemode is a setting which, if enabled, allows you to simply right-click a schematic block and the correct block will enter your hand, and then immediately be placed. Ordinarily, you would of course need to put the block in your hotbar, and then place it down. easyplacemode just cuts out the process of moving it from your inventory into the hotbar.
While the process of moving a single block from inventory to hotbar isn't long, easyplacemode makes the building process much quicker in a build where you would need to go through the process hundreds or thousands of times. You can just store all the blocks you'll need for the build in your inventory, and go along and right-click all the schematic blocks.
- It does not automatically place down blocks, like a bot would.
- It does not align or position blocks in the correct direction.
- It does not take blocks out of shulker boxes.
- It does not have any kind of benefit outside of building, such as PvP or finding bases.
- It does, however, allow you to place blocks against air. Seeing as this is obviously impossible in vanilla, Yukar let me know last year that doing this isn't allowed.
As far as I'm aware, the rules haven't been changed - you're still not allowed to do anything that a vanilla client can't also achieve.