What do "Player Score" & "Military Strength" mean under Domination Victory?

The player score is a metric to compare how well civilizations are doing. According to this civfanatics forum post, player score is calculated by

+2 for each tech and civic
+5 For each wonder
+3 for each great person (awarded on recieving GP)
+4 for a pantheon and +8 for a religion (not much value for using religion)

Empire seems to consists of
+5 per city
+1 per population
+3 per district

Military strength is a metric for comparing how strong a civilizations military is. According to this civfantics forum post, it's calculated by the sum of the strengths of the units you have.