Tactics
Zugzwang
A position where every legal move makes things worse, and the obligation to move is itself what loses. It is the one part of chess where you would rather pass, and it decides an enormous number of endgames: the whole technique of king and pawn play is arranging for the other side to be the one on move.
How to spot it
Count your opponent's moves rather than their material. When the pieces are frozen and only the king or a pawn can legally move, ask what happens after each of those and you will often find they all lose. Waiting moves are the tool, and a spare pawn move is worth keeping for exactly this.
The positions
Easiest first. Every one is from a real game, and the rating under each board is what it costs the players who have tried it on lichess.
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1. White to play Play it out →Answer
70.exd4 Kg5 71.d5 Kf5 72.d6
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2. Black to play Play it out →Answer
60...Kh4 61.Kg6 Kg3 62.Kxg5 Kxf3 63.Kh4 Kg2 64.Ne5 h2
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3. Black to play Play it out →Answer
60...Kf7 61.b4 axb4 62.a5 b3 63.a6 b2 64.a7 b1=Q 65.a8=Q Qb2#
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4. Black to play Play it out →Answer
35...Kd4 36.Ke2 Kc3 37.b4 axb4 38.axb4 Kxb4
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5. Black to play Play it out →Answer
38...axb6 39.f3 c5+ 40.bxc5 bxc5+ 41.Kxc5 Kxe5
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6. White to play Play it out →Answer
51.Kc2 h5 52.g5 h4 53.g6 h3 54.g7 h2 55.g8=Q h1=Q 56.Qg7#
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7. White to play Play it out →Answer
42.e5 Kc5 43.Ke4
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8. Black to play Play it out →Answer
55...Kf7 56.b4 axb4 57.a5 b3 58.a6 b2 59.a7 b1=Q 60.a8=Q Qb2#
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9. White to play Play it out →Answer
56.Kc2 g5 57.hxg5 h4 58.g6 h3 59.g7 h2 60.g8=Q h1=Q 61.Qg7#
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10. White to play Play it out →Answer
50.Qxb1+ Kxb1 51.Kd3 Ka2 52.Ke4 Ka3 53.Kd5 Kb4 54.h4 g5 55.h5
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11. White to play Play it out →Answer
33.g4+ hxg4+ 34.Kg3 g5 35.fxg5 fxg5 36.h5
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12. White to play Play it out →Answer
44.Kh4 hxg4 45.Kxg4 Ke6 46.Kg5
Reading about a pattern is the easy half. Motify finds the positions where you missed one, by running your own lichess and Chess.com games through Stockfish, and puts each of them behind two or three puzzles on the same idea so you meet it having just found it three times. See how Motify works.
Positions from the lichess puzzle database, released under CC0.