Basics are, in MTTs and SnGs, each registrant starts off with their own share of $Ev(equity) of the prize pool and given various factors like skill level of individual and playing style/skill of opponents each individual player will have their own personally sized expected piece of the pie. each time someone is eliminated all other participants gain the $Ev that is left behind (whatever their share was.
equity when we talk in terms of tournaments usually refers to how much of the prize pool your stack is worth at any given time... this uised to be worked out using the chip chop method.. but it had its obvious flaws. so they developed ICM to counter these problems... One key concept is this though.. when you win a tournament you only win a certain % of the prize pool. all the equity is based of that.
but assuming equal skill level.. at the start of a tournament everyone starst off the with same amount of equity. then after the first hand that changes, as someone gains chip and someone loses chips.. but yes.. that is not really true as some players with higher skill actually have more equity if they think they are better than most of the field.. so his chips are actually worth more than some novice whos never played before..
If say you are fresh into a 9 seat SnG, have QQ and super LAG raises all in just like his last 4 hands. You have 1500 chips and villain has 1600ish. This is a +cEv call. However it is possibly a -$Ev call because you are risking your entire equity on this call, depends on villains, albeit loose, range.
early on with QQ this is usually both plus Cev and +$EV to get it in with Queens.. depends on your stake of playing sng.. say your on the bubble and a big stack raises you all in.. you have the same QQ,, then its more likely to be +cEV and -$EV
Say you and villain have identical stacks and villain shoves into you on the button with QQ. We'll say first hand of the tourney. If you call and win you gain his chips but his equity gets distributed amongst all other participants. You doubled your chips but your equity does not now double.
Basically you risk your entire tournament equity for only part of villains.
The equity odds are not favorable for the call.
The first hand of the tourney a small % of equity is distributed.. in later stages.. its personified and becomes a massive spew of equity if say you shove and get called on the bubble..
Well, not for you anyways, only for your tablemates your call is +++$Ev. In that situation (early tourney) calling with less than KK is not recommended. They gain equity for no risk.
This is true for STT but with MTT were only concerned with CEV,, only at the final table are we concerned about $EV
Later in the tourney and ITM calling with QQ on shorthanded table, there, is +$EV. In the end game shoving a -cEv hand is many times +$Ev.
If you are not a tourney player, I am sorry if I may have confused things here, because tourney cEv/$Ev decisions are f*@%ing confusing when you start to work with them... hence why many can't go between Ring and cash.
tourney players are only concerned with accumulating chips, so its cEV.
If you are a tourney player, Colin Moshman's SnG book explains the cEV/$EV situation pretty well and you should read it if you can.
Hope this helps.
Good Luck