"I have apples."
Translation:У меня есть яблоки.
There is a slight difference in meaning (есть emphasises the existance of the apples), but they're indistinguishable when trying to translate a sentence without context. So neither is incorrect, and it annoys me quite a lot how I get streaks ruined by having to guess which of the meanings Duolingo meant.
When transliterating Russian, the apostrophe stands for the Russian letter ь. The ь is called the soft sign and indicates that the consonant preceding it should be softened/palatalized, thus affecting the pronunciation of the word. So then est (ест) and est' (есть) have different pronunciations and completely different meanings. The first is the he/she/it conjugation of the verb "to eat" and the second means "there is/are" so as you can see the apostrophe is pretty important.
Note: In case you're confused, u menya est' (у меня есть) literally translates to "by me there is" and is the most common way of saying "I have (something)" in Russian.
It’s written in Cyrillic: apostrophe represents the soft sign (ь). With the soft sign, «есть» means '(there) is/are/am', it's a copula (you can hear the pronounciation here). Without the soft sign, «ест» means 'eats/is eating' (pronounciation here).
The soft sign (represented by the apostrophe) changes the pronounciation of the preceding consonant to palatised. We call the «ть» a soft version of «т», and «т» is the hard version of the sound. English doesn’t have this distinction, but soft consonants are similar to slender consonants in Irish.