RP
What's the most common type of endgame??

Silman's Complete Endgame Course is written with an intention to help readers with the stuff that they are most likely to need.
http://theweekinchess.com/john-watson-reviews/theres-an-end-to-it-all
https://web.archive.org/web/20140708103149/http://www.chesscafe.com/text/review594.pdf

Endgame frequency table
(Source: https://thechessworld.com/articles/endgame/chess-statistics-most-often-occuring-endgames-in-chess/)
Percent
White Pieces
Black Pieces
8.45 rook rook 6.76 rook & bishop rook & knight 3.45 two rooks two rooks 3.37 rook & bishop rook & bishop (same color) 3.29 bishop knight 3.09 rook & knight rook & knight 2.87 king & pawns king (and pawns) 1.92 rook & bishop rook & bishop (opposite color) 1.87 queen queen 1.77 rook & bishop rook 1.65 bishop bishop (same color) 1.56 knight knight 1.51 rook bishop 1.42 rook & knight rook 1.11 bishop bishop (opposite color) 1.01 bishop pawns 0.97 rook knight 0.92 knight pawns 0.90 queen & minor piece queen 0.81 rook two minor pieces 0.75 rook pawns 0.69 queen rook & minor piece 0.67 rook & pawn rook 0.56 rook & two pawns rook 0.42 queen pawns 0.40 queen rook 0.31 queen two rooks 0.23 king & one pawn king 0.17 queen minor piece 0.09 queen & one pawn queen 0.08 queen two minor pieces 0.02 bishop & knight king 0.01 queen three minor piecesAgreed!
I think it is the king and pawn endgame.