Inserters are the fundamental structures of a factory, and are a vital component in almost all contraptions. They look and work like a robot-arm and take items from behind and place them in front of it, if the object in front of it has enough space to accomodate for it.
Inserters will act differently depending on what they are moving items to/into so as not to monopolize all of the items being picked up and allow other machines and inserters on the same transport belt to have items.
Insertion Limits
Inserters will not insert into certain buildings if they already have, or are above of, a certain amount of items; it will simply seize to function until space has been made, and it will resume insertion.
For example, if a boiler has 5 or more pieces of fuel in it, then an inserter will not insert additional fuel until it has 4 or less.
An inserter, which takes items from a chest or another assembly (anything, which has Storage/Stacks), can overfill due to the Inserter item stack size. The same happens, if you load with more than one inserter.
Inserters and transport belts
Inserters will always place the item on the further lane.
