Quick answer
Э э is the e of “pet”, with no y-sound in front. Е is the same vowel plus a y-glide, and it softens the consonant before it.
e
How to say it
Say “echo”, stopping on the first vowel. That is Э — open, flat, no glide.
Э or Е?
Э́то versus е́сли: the first begins with a bare vowel, the second with a y. At the start of a word the difference is audible; inside a word Э appears almost only in loanwords and after a vowel: поэ́т, дуэ́т.
Э in borrowings
Russian often writes Е where English hears a plain e — тест, компью́тер, интерне́т — while the preceding consonant stays hard anyway. Э is reserved mostly for word-initial position: эта́ж, эта́п, эффе́кт.
Typical mistakes
Reading э́то as “yeto”
“éto”
Э has no y-glide — that is Е.
Confusing Э with З
Э opens right, З opens left
They are mirror images.
Check yourself
Which word contains Э?