Pulling is the act of luring neutral creeps into following your hero. This can be done for two reasons.
The first one is stacking - using the set spawntimes to create bigger creepcamps. To read about stacking, see Stacking.
The second reason is to halt your creeps and thereby pull the creepline closer to your own defences. This article mainly concerns itself with the latter reason, but the two ways of pulling are often used in succession.
Pulling the lane
In Dota 2 it is possible to lure out the neutral creeps living in your jungle. If you attack or closely approach them, they will respond by attacking you. If you then run away, they will chase you for a short distance. If done correctly, you can have these creeps chase you all the way to your lane. Upon encountering the neutral creeps, your own creeps will halt their advance along the lane and will try to defend you from these aggressors first. They will chase the neutral creeps back to their camps and fight them, thereby taking a lot of damage or even dying. Using your lane creeps to tank the incoming damage makes it easier to kill neutral creeps early on, and thus pulling introduces new money and experience to the game that would otherwise be left untapped. As a consequence, these creeps will not advance towards your opponent's creeps, leaving their advance unhindered. The creepline will move closer to your own tower, giving the carry hero of that lane a safe way to farm gold and experience. Additionally, redirecting your lane creeps to the jungle - where they should be killed by neutral creeps - potentially denies the enemy team the opportunity to last hit an entire creep wave, hindering their ability to gain gold and experience.
This technique is a staple skill in the arsenal of any lane support heroes.
A video outlining this can be seen here: <embedvideo service="youtube">https://www.youtube.com/watch?v=PJAfTVqFL6g</embedvideo>
Your creeps spawn at the XX:00 and XX:30 mark - twice every minute. After spawning they will take a while to move along the lane. Neutral creeps can only be pulled to the lane at certain points, and moreover they will take some time to get there. To do a successful pull, these two events must coincide - the neutral creeps should arrive in your lane at the same time your own creeps do.
When you follow this line of reasoning the other way around, we end up with set times at which you can attack the creeps to make them bump into your own perfectly. These times are listed in the figure below.