Hit confirmation, often shortened to hit confirm, is a term used in fighting games to refer to the process of discovering if a combo is safe to continue.
When hit confirming, a player must essentially pay attention to whether or not a given move at a certain point in the combo they are attempting to put together hits; from there, the player has to visually see if it successfully hit the opponent and plan their followups accordingly. On hit stronger Comboes can be performed and on block the player can try to pressure further or Tick Throw
Generally, the 'confirming' move is one that is either safe or positive (meaning the player can move before the opponent) on block. This is necessary as if the confirm attack is negative on block the player can be punished. It is recommended that players learn their individual character's "pressure" attacks. Overheads can be a gamble for some characters as they can be negative on block but can be comboed on hit, others are just single hit and can not be followed up on.
Pressure refers to a tactic of using multiple safe on block attacks to keep the opponent on their toes. Usually Link comboes are safe on block. When performing blockstrings (consecutive safe on block attacks to pressure the opponent), the player should vary between throwing, overheads (if applicable), Dive Kicks (if applicable) and throws. Opponents may try to mash out attacks or even throw out Reversals, pressuring players should try and find the opponent habbits and bait out unsafe reversals or make the opponent to try and mash normals so they get Counter Hit and receive big damage once an attack hits.
Bread and Butter Combo Edit
A Bread and Butter Combo refers to a combo that characters can do that is usually 100% safe, or very safe, regardless if the sequence is blocked. An easy example is Ryu's Crouching MK into HP Hadouken. This is especially true pre Street Fighter V as it was a "True" block string at most ranges. These combos can reduce the need for hit confirming at the cost of usually doing less damage overall.