Just in pronunciation. "ê" is pronounced like "è" and it's the same as the "ai" in the words 'lait' or 'mais' for example.
"é" is the same as the interjection 'hé'
"e" is the most complicated one: depends of its place.
- Silent at the end of the word,
- Works like "è" before some consonants like r (perdre), or double consonants (poussette, mademoiselle)
- But like "é" when behind a verb stem: chercher is said "chairché" , aller "allé".
- Or is said like the French word 'an' when associated with nt (entendre), ns (ensemble), mp (empêcher) ou mb (emboîter), and probably others I forgot.