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Why is it that Lichess, and other engines for that matter, give a non-zero evaluation score on an endgame position that should be either a draw or a win for one of the sides (given perfect play)? For example, the position below returns an evaluation score of -0.5 when there doesn't seem to be enough material for black to achieve a victory.
[FEN "6r1/8/8/8/3k1K2/R2b4/8/8 w - - 0 1"]
Unless you explicitly hard-code these endgames, or provide the computer with endgame tablebases, they will apply what they've always done throughout the game: search lines and return the static eval (which is basically the evaluation function of the engine, evaluated on the final position). The static eval isn't smart enough to realize that this game is a draw - keep in mind the static eval is supposed to work for all positions, so it's not surprising that it doesn't return a completely accurate score for this one. Accordingly the computer flatlines at -0.50, until the 50-move rule helps it prune to a draw.
In Lichess, you have 2 separate features: computer analysis and endgame tablebases. Scores are always shown using the computer analysis feature, but at the endgame you can also see the tablebases features, available for 6-men endings I think. If you open this component, you will see each winning/drawing/losing move together with their DTZ (distance to zeroing the 50-moves rule) and DTM (distance to mate).
