1.15 Updating tile entities

Hello, I have some questions about the methods that are used for example to update tile entities for the client. I have made some simple TEs that can hold a single Item which then gets displayed using a TESR.

I have red on this forum that you need the update tag methods and the packet methods but I dont understand what the tag methods are for. Also when I change something about the TE I have to call 

		this.world.markBlockRangeForRenderUpdate(this.pos, this.getBlockState(), this.getBlockState());
		this.world.notifyBlockUpdate(this.pos, this.getBlockState(), this.getBlockState(), 3);
		super.markDirty();

and I dont really know what all of these methods do, when I have to use them and when I dont (this part is especially important). Could somebody please explain that to me? Thanks in advance