The form ест ((s)he eats) is always Thir Person Present Tense Singular from the verb есть and so forever shall it be. It is therefore very different from the form есть

(Yes, the Palatalisation (that nowadays unpronounced soft sign at the end of the verb) does matter in Russian phonetics).

But, again, the form есть is a homonym for

a) infinitive form of есть (to eat) and

b) Third Person Present Tense Singular copula verb есть ('to be', but also used as 'to have' in 'A has B'-type structures.

So in fact you have to distingwish between all the three (unless you will additionally want to know why in certain structures of A-has-B-type Russian speakers prefer to use this form and in other cases of the same structures they omit the verb completely, e.g. what is a difference between the phrases 'У меня есть машина'; 'У меня - машина' and 'Машина - у меня').

The form ест ((s)he eats) is always third person present singular from the verb есть and so forever shall it be. It is therefore very different from the form есть.

(Yes, the palatalisation (that nowadays unpronounced soft sign at the end of the verb) does matter in Russian phonetics).

But, again, the form есть is a homonym of

a) the infinitive form of есть (to eat) and

b) the third person present singular copula verb есть ('to be', but also used as 'to have' in 'A has B'-type structures.

So, in fact, you have to distinguish between all three (unless you also want to know why in certain structures of the A-has-B-type, Russian speakers prefer to use this form, and in other cases of the same structures, they omit the verb completely, e.g. what's the difference between the phrases 'У меня есть машина'; 'У меня - машина' and 'Машина - у меня').