En el encabezado del informe, mi tutora escribió la fecha y el título.

Because de + el contracts to del in Spanish.

So:

• de el informe → del informe

This contraction is required with de + el.
The only common exception is when el is part of a proper name, such as de El Escorial.

En is the preposition here, and el encabezado is the noun phrase.

• en = in / on / at, depending on context
• el encabezado = the header / heading

In Spanish, en is often used where English might say in or on. With documents, en el encabezado is a natural way to say in the header or at the top heading area.

Also, Spanish normally includes the definite article here: el encabezado, not just encabezado.

Here, encabezado means the header or heading section of the report.

It is not the same as título:

• encabezado = the top section/header
• título = the title itself

So the sentence is saying that in the top/header part of the report, the tutor wrote the date and the title.

Tutora is the feminine form of tutor.

In Spain, it can mean different things depending on context, for example:

• a school tutor or form tutor
• an academic supervisor
• a teacher responsible for a student’s guidance
• sometimes a tutor in the general sense

So mi tutora means the speaker has a female tutor/supervisor/teacher-guide.

Because mi is the normal possessive adjective used before a noun:

• mi tutora = my tutor

Mía is a possessive pronoun or a stressed possessive form, and it does not go before the noun in this way.

Compare:

• mi tutora = my tutor
• la tutora es mía = the tutor is mine

Also, mi does not change for masculine or feminine singular nouns:

• mi tutor
• mi tutora

Because the noun shows the gender, not the possessive adjective mi.

• tutor = masculine
• tutora = feminine

But:

• mi = my, for both masculine and feminine singular nouns

So:

• mi tutor
• mi tutora

This is different from articles like el and la, which do change for gender.

Escribió is the preterite tense, third person singular, from escribir.

• escribir = to write
• escribió = he/she wrote

The preterite is used for a completed action in the past.
Here, it presents the writing as a finished event.

So the sentence treats the action as something that happened and was completed.

Because escribió and escribía give different past-time meanings.

• escribió = wrote, as a completed action
• escribía = was writing / used to write / wrote habitually

In this sentence, the tutor wrote the date and title as a specific finished action, so escribió is the natural choice.

If you said escribía, it would sound more like background description, repetition, or an ongoing action in the past.

They show the correct stress.

• escribió: the accent on ó shows the stress falls on the last syllable: es-cri-bi-ó
• título: this is stressed as TÍ-tu-lo, and because it is an esdrújula word, it must always have a written accent

Without the accent marks, the words would follow different default stress rules and be pronounced incorrectly.

Spanish often repeats the definite article with each noun in a list when referring to specific things.

So:

• la fecha y el título

is very natural and clear.

In English, we often say the date and title with only one the, but Spanish commonly keeps the article before both nouns, especially when they are understood as separate items.

It is natural and helpful, but it is not always absolutely required in every similar sentence.

The phrase En el encabezado del informe is an introductory element placed before the main clause, and the comma marks a pause:

• En el encabezado del informe, mi tutora escribió...

In Spanish, commas after fronted introductory phrases are often used when the phrase is a bit long or when the writer wants a clear break. This sentence reads very smoothly with the comma.

Yes. Spanish word order is more flexible than English.

The neutral order here is:

• Mi tutora escribió la fecha y el título.

With the introductory phrase added:

• En el encabezado del informe, mi tutora escribió la fecha y el título.

But Spanish could move elements around for emphasis or style, for example:

• Mi tutora escribió la fecha y el título en el encabezado del informe.
• Escribió la fecha y el título mi tutora. — possible, but less neutral

The original version sounds natural and straightforward.

Because Spanish nouns have grammatical gender, and the article must match the noun.

In this sentence:

• el informe = masculine
• el encabezado = masculine
• el título = masculine
• la fecha = feminine

You generally have to learn the gender with each noun. Some endings help, but they are not perfect rules. For example:

• -o often masculine
• -a often feminine

Here, those patterns work:

• encabezado, título, informe → masculine
• fecha → feminine