The execution turn metric (ETM), is a metric for the 3x3x3 where any perceived movement counts as a turn; this includes rotations. Therefore, the interpretation of this metric can be somewhat subjective. For example, U2 can be either 1 or 2 moves.
ETM was designed for measuring 'true' TPS by David Woner. It is intended mainly for reconstructions, where videos are available to see how many movements were actually performed.
Example reconstruction ETM count
Scramble: L2 R2 U2 L2 U F2 L2 F2 U L B2 F' R B2 U' B F L F2 D'
Cross: L2 u R' F' (4 ETM, obvious)
F2L 1: L' U' L d R' U R (7 ETM, obvious)
F2L 2: y' R U' R' U2 R U' R' (8 ETM, rotation requires regrip so it is counted)
F2L 3+4: y L U2 L' R U R' (7 ETM, rotation counts, L' R counts as two moves not one, because it is performed as such)
OLL: M U' M' U' U' M U' M' (8 ETM, Slice moves are performed as slices here. The U2 is two flicks with the left index, thus two moves.
PLL: R' U2 R U' U' R' F R U R' U' R' F' R2 U' (15 ETM, the first U2 is an index-middle double flick with the right hand, thus one move. The second is two left indexes again, thus two. R2 is a single wrist turn, thus one.)
Total solve: 56 QTM/49 HTM/44 STM/49 ETM