Understanding your win condition is hard. Broadly speaking there are 4 types of deck aggro, midrange, control and combo, (tempo decks fit somewhere between aggro and midrange). Aggro deck tend to try to get early damage in with minions but tend lose the board and have to finish off the game with direct damage spells, they usually want to win by turn 6, and don't care about playing the value game; notable Aggro decks are Facehunter, aggro paladin and Aggro shaman. Midrange decks try to take the board early to midgame (turn 1-3/4) and sustain that board control to victory on turn 7-13, more controlly midrange like midrange pally care about card advantage more whilst tempo-ish decks like midrange hunter or secret pally care more about strong turns at the expense of future value, tempo decks tend to run a few damage spells although this is by no means a hard and fast rule. Control tries to survive the early turns to swing the board and win in the lategame turn 9+, they tend to run lots of spells to deal with the enemies most threatening minions, the minions they run are either finishers like grommash or serve to aid survival like sludge belcher, northshire cleric and armoursmith; control deck's main early aim is to survive as efficiently as possible they need their card advantage to win; against aggro you tend to let your hand size drop more than vs control, notable control decks are control priest, control warrior and handlock. Combo decks are exactly what you would expect, they have a certain combo of cards that when played together close out games very quickly, combo decks can be control midrange or even aggro(sort of) although most often the are control, notable combo decks are combo druid(midrange), freezemage(control), combolock(control), murloc paladin(control) and aggro mage(aggro but runs icelance to combo with frostbolt). There is one other win condition, getting your opponent to fatigue, there are currently very few decks that try to win this way: mill rogue, fatigue priest, fatigue warrior and fatigue druid. Fatigue is basically super control aiming to run through all your opponent's deck and then win because they are further into fatigue or you have more armour. Mill is more aggressive, you try to burn cards from your opponent's deck by their hand reaching the max 10 cards and them drawing more whilst also bringing them to fatigue very quickly and again winning due to them being deeper into fatigue.

Some decks have much more complicated gameplans than what is described notable patron warrior but this should be a good starting point in knowing what your deck is aiming to do.