Tank Diff
A state where the matchup and skill gap between the lone tanks in 5v5 dictates the outcome of the entire match.
Unlike the 6v6 era, in 5v5 the tank is a single slot, so the result of the tank matchup carries more weight in its impact on the match than any other role. Getting the counterpick out first against the enemy tank to make the matchup favorable, how the supports split their attention over which tank to prioritize caring for, when to take the initiative back with a tank swap — these dictate how everyone moves and how efficiently Ults are spent. It gets mocked as "a tank game", but in a coach / IGL context it is treated as the central macro problem of "getting the tank matchup into a winnable state". When the space and defensive line the tank creates break down, the effect ripples out across everything the DPS and supports do, which makes it one of the axes you have to read earliest when judging who holds the initiative in the match.
When the enemy tank's counterpick is landing and the losing matchup keeps repeating, recognize that "a tank diff is happening" as the trigger for a swap decision. Also used as the axis for weighting support heal allocation and the DPS's priority target toward the enemy tank.
Holding the same hero through a losing tank matchup and giving up space every fight. Or over-prioritizing "beat it with player skill" while the counterpick is clearly landing, so the swap call comes too late.
Space
Physical control over the favorable parts of the map — high ground, routes, sightlines.
Resource Trade
Spending a minor cooldown to force a major defensive one, netting an advantage for the real fight.
Tempo
The initiative — who gets to choose when and on whose terms the next fight starts.