Can Anyone Explain The Math Behind Poison, Lifesteal And Such?

I am really confused right now. I come from a game, where Lifesteal gives you a % of dmg you dealt to an enemy as health back, and poison is just an effect that lasts for a couple of seconds, doing dmg every second.

Now, i get confronted with 6/4s Lifesteal or 21/3s Poison. What does that even mean?

Im sorry if this question is not necesarry, because its self-explanatory to most people, but to me its not.
Btw, i tired to look this up on the wiki but i didnt find anything.

 

21/3s poison means you do 21 damage over 3 seconds, or a 7 damage hit every second

6/4s life steal means that sometimes when you hit (happens less often for faster weapons) you will regen 6 hp

the 4 in this actually doesn't mean anything and tbh i don't know why it's there

 

Let's start with poison. The /3s means that the effect is applied over 3 seconds. This means that your damage hits 3 times, for one third of the poison damage each hit. So if you have 6/3s poison, after hitting an enemy, you will deal 2 damage per tick, every 1 second for 3 seconds to get that 6 damage

Life/mana steal is more complicated...
Basically the /4s is about how often it will activate on a melee hit. This means the chances are higher with slower weapons. It doesn't trigger off of spells, expect for warriors war scream.

 

Thank you guys! Now it makes sense :)