An internal conflict refers to a conflict that takes place within one character. It refers to the problems the character is facing as well as the moral dilemmas. Internal conflict also refers to the choices a character makes. We see one example of internal conflict with respect to Helena in the very first scene. After Hermia and Lysander inform her of their plans to escape from Athens and meet in the woods, Helena makes the conscious decision to betray her childhood friend by telling Demetrius of their plans. We know that Hermia's friendship is important to her because, later, when she believes that Hermia is mocking her, we see her ask Hermia how she could possibly forget their friendship and talk about how they shared everything together, such as the same sewing "sampler," the same "cushion," all while singing the same "song" (III.ii.204-209). Hence, we know that Helena has a momentary struggle with herself in her decision to betray her friend. We also see evidence of this struggle when Helena convinces herself that it is worth it, even if all she receives as a reward is thanks from Demetrius. She claims that just having him look at her makes her deception worthwhile, as we see in her lines:
...and for this intelligence
If i have thanks, it is a dear expense.
But herein mean I to enrich my pain,
To have his sight thither and back again. (I.i.253-256)
Hence, we see that one internal conflict in the book is that Helena had a momentary struggle with herself before deciding to betray her best friend.
An external conflict is a fight or disagreement that happens between two characters, or even two groups of characters. We also see an external conflict with respect to Helena and Demetrius. Helena is still in love with Demetrius and still insists on pursuing him, even though he claims to hate her and is pursuing Hermia. Since Helena wants Demetrius to love her again, but Demetrius disagrees with this, we can see that their relationship is an example of external conflict. In fact Helena's and Demetrius's external conflict is even portrayed in verbal fights between the two characters, fights in which Demetrius even threatens Helena with physical violence. We see the threat of physical violence implied in his lines, "Tempt not too much the hatred of my spirit; / For I am sick when I do look on thee" (II.i.215-216).