Their names are Demetrius, Lysander, Hermia and Helena. At the start of the play Hermia is betrothed to Demetrius but in love with Lysander, who returns her love. Helena is in love with Demetrius, who claimed to love her, until he met Hermia. ('Until he looked on Hermia's eyne / He rained down oaths that he was only mine')
Through a series of misadventures (including a magic spell planned by the king of the fairies (Oberon), but bungled by his assistant (Puck) all the lovers end up in the woods together on a Midsummer night, and both Demetrius and Lysander fall in love with Helena. After several confrontations, and much hilarity on the part of the audience, the spell is removed from all but Demetrius, and at the end of the play Demetrius marries Helena and Lysander marries Hermia on the same day as the Duke of Athens (Theseus) and his Amazon queen, and the fairies bless all three unions.
Lysander,and Demetrius are the male suitors; Hermia and Helena are the female love interests. However, both Lysander and Demetrius are in love with Hermia.
For her part, Hermia is in love with Lysander. However, her father Egeus, in service to the Duke of Athens, demands in the Duke's presence that his daughter is to wed Demetrius. She will do so, he orders, or face grim alternatives, death or a nunnery.
It is all bad news for Helena, who is in love with Demetrius herself, although he has jilted her; jealously, she tells Demetrius of Hermia and Lysander's plot to escape her father's wishes.
Through a series of comical plot twists largely due to mischievous fairies, all is well in the end, with Lysander and Hermia finally uniting and Helena and Demetrius in love.
Hermia and Lysander, and Helena and Demetrius are the young aristocratic lovers. Although Demetrius and Hermia are more aristocratic than the others. (which is why Hermia's father is insistent that she marries Demetrius rather than Lysander)
They are Lysander, Demetrius, Helena, and Hermia…and a list is about all the detail we get to distinguish among them.
More seriously, we learn that early in the play, Hermia wants Lysander, but her father wants her to marry Demetrius. Demetrius had in the past courted Helena, and won her heart, but now rejects her in favor of Hermia. In the end, Hermia and Lysander end up together, and Demetrius and Helena.