The basic verb in Russian that means “to eat” is есть/съесть. Notice that the second letter of the perfective forms is a hard sign, not a soft sign. This is one of the four most irregular verb stems in the language. (The others are the stems of дать, хотеть and бежать.)

There are a couple potentially confusing points here. Notice first of all that the imperfective infinitive is spelled the same as есть, that quirky present tense form of “to be” that appears in “there is/are” and “have” sentences.

The next trick is that есть is actually pronounced differently from ест. In both words the first sound is a y sound as in yes, but the vowel quality is different:

Here are a couple sentences where you can hear the difference:

As to the grammar of the verb, the thing that you eat shows up in the accusative case:

In English we often say things like “I ate breakfast/lunch/dinner,” and in Russian theoretically it's grammatical to say things like «Я (съ)ел завтрак/обед/ужин.» But frankly the Russians rarely say that. Instead they subsitute the verbs that directly address those meals: «Мы (по)завтракалали/(по)обедали/(по)ужинали».

* The careful student may notice that in this sentence the accusative plural акриды copies the nominative plural, which is atypical for modern Russian. Animate accusative plurals did not always automatically copy the genitive. This change began hundreds of years ago with words referring to male human beings, and then it eventually spread to other noun classes. That process is nearly complete in modern Russian, although there are still a few constructions where animate nouns sometimes occur in the accusative plural in a form that copies the nominative.