בהתחלה לא הבנתי את המילה הזאת, אבל אחר כך המורה הסבירה לי את הפירוש שלה.

בהתחלה is made of:

• ב־ = in / at
• התחלה = the beginning

So literally it is at the beginning or in the beginning.

In Hebrew, short prepositions like ב־ often attach directly to the following word. Since the noun is definite (the beginning), the form becomes בהתחלה rather than writing the words separately.

Hebrew verbs usually already show the subject, so the subject pronoun is often omitted.

• הבנתי = I understood
• לא הבנתי = I did not understand

The ending ־תי tells you the subject is I, so אני is unnecessary unless you want extra emphasis.

את is the direct object marker. It appears before a definite direct object.

Here, המילה הזאת = this word, which is definite, so Hebrew uses את:

• הבנתי את המילה הזאת = I understood this word

Important: את here does not mean you. It is a completely different word with a different function.

A good rule:

• use את before a specific/definite object
• do not translate it into English

In Hebrew, demonstratives like this usually come after the noun:

• המילה הזאת = this word
• הספר הזה = this book
• הילדה הזאת = this girl

So Hebrew says something more like the word this.

Also notice that both parts match in gender:

• מילה is feminine
• so the demonstrative is זאת

Because מילה is a feminine noun.

Hebrew demonstratives must agree with the noun:

• masculine singular: זה
• feminine singular: זאת

So:

• הספר הזה = this book
• המילה הזאת = this word

Even though the thing is not biologically female, grammatical gender still matters.

They are time expressions that set the sequence of events:

• בהתחלה = at first / in the beginning
• אחר כך = afterwards / later / then

So the sentence is structured as:

1. At first I didn’t understand the word
2. Later the teacher explained its meaning to me

These expressions are very common in narration.

Because the verb agrees with the teacher’s gender.

• הסבירה = she explained
• הסביר = he explained

The noun מורה can refer to either a male or female teacher, so the verb tells you which one it is here. Since the sentence says הסבירה, the teacher is female.

לי means to me.

It is made from:

• ל־ = to
• י = me

So:

• המורה הסבירה לי = the teacher explained to me

Hebrew often uses this kind of attached preposition:

• לי = to me
• לך = to you
• לו = to him
• לה = to her

Because the teacher did not explain the word itself; she explained its meaning.

• אותה would mean it/her
• but את הפירוש שלה means its meaning or its explanation

So the sentence specifically says that what was explained was the meaning of the word, not the word as an object by itself.

שלה means of her / hers / its, depending on context.

Here it refers back to המילה (the word), which is feminine, so:

• הפירוש שלה = its meaning
  literally: the meaning of it

Because מילה is grammatically feminine, Hebrew uses שלה.

Compare:

• הספר... הפירוש שלו would sound odd because book is masculine, so the pronoun would be שלו
• המילה... הפירוש שלה uses שלה because word here is feminine

ה־ is the Hebrew definite article, meaning the.

So:

• מילה = a word / word

• המילה = the word

• מורה = a teacher / teacher

• המורה = the teacher

• פירוש = meaning / interpretation
• הפירוש = the meaning

Hebrew attaches the directly to the beginning of the noun instead of writing it as a separate word.

Not exactly.

פירוש usually means:

• meaning
• explanation
• interpretation

In this sentence, הפירוש שלה means its meaning.

That is different from translation, which would usually be תרגום.

So if you did not understand the word, the teacher explained what it means, not necessarily how to translate it.

Both are in the past tense.

• הבנתי = I understood
• הסבירה = she explained

Hebrew past-tense verbs change according to person, number, and often gender.

In this sentence:

• הבנתי = first person singular
• הסבירה = third person singular feminine

It is fairly close to English, but there are some very Hebrew features.

The overall structure is:

• בהתחלה = at first
• לא הבנתי = I didn’t understand
• את המילה הזאת = this word
• אבל אחר כך = but afterwards
• המורה הסבירה לי = the teacher explained to me
• את הפירוש שלה = its meaning

What feels most different from English is:

• the use of את
• the demonstrative after the noun: המילה הזאת
• possession with שלה
• the fact that subject pronouns are often omitted

So the sentence is not hard structurally, but it contains several very common Hebrew grammar patterns.

Yes. A few common variations are possible, for example:

• בהתחלה לא הבנתי את המילה הזו, אבל אחר כך המורה הסבירה לי את הפירוש שלה.
• בהתחלה לא הבנתי את המילה הזאת, אבל אחר כך המורה הסבירה לי מה היא אומרת.

A couple of notes:

• הזאת and הזו can both mean this in this position, though הזאת is very common in standard learner materials.
• מה היא אומרת literally means what it says/means, which is often a more conversational way to express the idea.

The original sentence is perfectly natural and clear.