Le compte bancaire est crédité aujourd’hui.

In French, singular count nouns usually need an article. So le compte bancaire means the bank account.

French uses articles more often than English does. Even where English might sometimes drop one, French usually keeps it.

Compte means account, and bancaire means bank-related or banking.

Together, compte bancaire is the standard way to say bank account.

Most French adjectives come after the noun, and bancaire is one of them.

So:

• un compte bancaire = a bank account
• literally, an account banking/bank-related

This is normal French word order.

Because this sentence is in the passive voice.

• La banque crédite le compte. = The bank credits the account.
  This is active: the bank does the action.

• Le compte bancaire est crédité. = The bank account is credited.
  This is passive: the account receives the action.

So est crédité is built with:

• est = present tense of être
• crédité = past participle of créditer

In banking, créditer means to credit an account, in other words to add money to it.

So if an account is crédité, money has been placed into it or recorded on the positive side of the account.

The opposite idea is débiter:

• créditer un compte = add money to an account
• débiter un compte = take money from an account / charge an account

Because it agrees with compte, which is masculine singular.

In a passive construction with être, the past participle agrees with the subject:

• masculine singular: crédité
• feminine singular: créditée
• masculine plural: crédités
• feminine plural: créditées

Since le compte is masculine singular, the correct form is crédité.

Grammatically, yes: est is in the present tense.

But in meaning, French present tense can be a little flexible. Depending on context, Le compte bancaire est crédité aujourd’hui can suggest:

• the account is being credited today
• the account gets credited today
• the account will be credited today

So it does not always mean the action is happening at this exact second. The word aujourd’hui helps place the event within today.

Time expressions often go at the end in French, especially when they give extra information after the main statement.

So:

• Le compte bancaire est crédité aujourd’hui.

is very natural.

You can also move it for emphasis:

• Aujourd’hui, le compte bancaire est crédité.

That puts more focus on today.

The difference is mainly about how the action is viewed.

• est crédité aujourd’hui
  present passive; it can sound like a current or scheduled process/state for today

• a été crédité aujourd’hui
  perfect/passé composé passive; it clearly says the account has been or was credited today

So if you want to emphasize completion, a été crédité aujourd’hui is often clearer.

Yes. That is completely possible if the context already makes it clear that you mean a bank account.

Adding bancaire just makes it more explicit:

• Le compte est crédité aujourd’hui. = the account is credited today
• Le compte bancaire est crédité aujourd’hui. = the bank account is credited today

Yes, in modern French aujourd’hui is written as one fixed expression.

The apostrophe is part of the standard spelling. Historically, the word developed from an older expression, but for learners the main thing is simply to memorize aujourd’hui as the normal word for today.

A simple English-friendly approximation is:

luh kont bon-KAIR ay cray-dee-tay oh-zhoor-DWEE

A few useful notes:

• le sounds like luh
• compte ends with a nasal vowel; the p is not really pronounced
• bancaire sounds roughly like bon-kair
• est is usually pronounced like ay
• crédité sounds like cray-dee-tay
• aujourd’hui sounds roughly like oh-zhoor-dwee

Yes, especially in formal, administrative, or banking contexts.

Because créditer un compte is a technical banking expression, the sentence sounds a bit formal or institutional rather than casual conversation. That is normal for financial language.