These dialogues contain the core concepts of Platonic philosophy and serve as a good introduction to the legacy of Socrates and philosophy in the golden age of Greece.
In the first of the dialogues Euthyphro and Socrates discuss and try to define allegiance. Euthyphro charges his father of murder of one of his workers; as Socrates is also being charged with impiety he hopes to learn a thing or two from Euthyphro.
Apology is Plato’s version of Socrates’s speech at his trial in his own defense.
Crito in the third dialogue discusses with Socrates the power of justice and offers to help Socrates escape from prison.
In Meno, Socrates and Meno cover virtue, and whether or not this is something that can be taught and if there is a common virtue in everyone.
And finally, Phaedo, who was present at Socrates’s death, relates what happened in his final moments.