La profesora usa un programa sencillo para mostrar gráficos en clase.

Because profesora is the feminine form of profesor.

• la profesora = a female teacher / the female teacher
• el profesor = a male teacher / the male teacher

Spanish nouns referring to people often change ending to match gender:

• profesor → male teacher
• profesora → female teacher

The article changes too:

• la with feminine singular nouns
• el with masculine singular nouns

In Spanish, nouns usually need an article much more often than in English. Here, la profesora means the teacher. Spanish does not usually drop the article in this kind of sentence.

So:

• La profesora usa... = The teacher uses...

This is completely natural Spanish, even though English may sometimes phrase things more flexibly.

This is a very common learner question. Although many nouns ending in -a are feminine, programa is masculine:

• el programa
• un programa

This happens because programa comes from a group of words of Greek origin that are often masculine in Spanish, such as:

• el problema
• el sistema
• el tema
• el idioma

So in the sentence, un programa sencillo is correct because both the article and adjective agree with the masculine noun programa.

Because the adjective must agree with the noun it describes.

Here, sencillo describes programa, and programa is masculine singular, so the adjective must also be masculine singular:

• un programa sencillo

Compare:

• un libro sencillo = a simple book
• una idea sencilla = a simple idea

Agreement is one of the most important patterns in Spanish grammar.

Usa is the third-person singular present tense form of usar.

Full present tense of usar:

• yo uso
• tú usas
• él/ella/usted usa
• nosotros/nosotras usamos
• vosotros/vosotras usáis
• ellos/ellas/ustedes usan

So La profesora usa... means The teacher uses...

In this sentence, usa matches la profesora, which is a third-person singular subject.

After para to express purpose, Spanish normally uses the infinitive.

So:

• para mostrar = to show
• literally: for showing / in order to show

This structure is very common:

• Estudia para aprender. = He/She studies to learn.
• Uso el móvil para trabajar. = I use the phone to work.
• La profesora usa un programa sencillo para mostrar gráficos.

So para + infinitive is the standard pattern for expressing purpose.

The written accent shows where the stress goes: GRÁ-fi-cos.

Without the accent, Spanish stress rules would make you expect the stress in a different place. The accent mark tells you that the stress falls on the first syllable.

Also, gráfico is a common word that can mean:

• graph
• chart
• sometimes graphic, depending on context

Here, mostrar gráficos usually means to show graphs/charts.

It depends on context. In a classroom sentence like this, gráficos usually means graphs or charts.

So:

• mostrar gráficos en clase most likely means show graphs/charts in class

In other contexts, gráfico/gráficos can also relate to graphics. Context tells you which meaning is intended.

En clase is a very common expression meaning in class or during class.

Spanish often leaves out the article in set expressions like this when talking about the activity or setting in a general way:

• en clase = in class
• en casa = at home
• en prisión = in prison

If you say en la clase, it can sound more like you mean a specific classroom or a specific lesson:

• en la clase de matemáticas = in the maths class
• en la clase = in the classroom / in that class

So in your sentence, en clase is the natural general expression.

The given order is the most neutral and natural:

• La profesora usa un programa sencillo para mostrar gráficos en clase.

But Spanish word order is somewhat flexible. For example, you could move parts for emphasis:

• En clase, la profesora usa un programa sencillo para mostrar gráficos.

That said, the original version is the best standard choice for learners because it is clear and natural.

Yes, that is also correct, but it shifts the focus slightly.

Compare:

• La profesora usa un programa sencillo para mostrar gráficos en clase.
  Focus: the teacher uses a simple program for a purpose.

• La profesora muestra gráficos en clase con un programa sencillo.
  Focus: the teacher shows graphs in class, and the program is the tool used.

Both are grammatical. The original sentence emphasizes the act of using a program.

In standard Spanish from Spain, usa is pronounced with a normal s sound, not like the English z in use.

Roughly:

• usa = OO-sa

Also, unlike English, the written u is a clear vowel sound, and each vowel is pronounced distinctly.

Usually, yes. Sencillo often means simple, basic, or straightforward.

In this sentence:

• un programa sencillo = a simple program

Depending on context, sencillo can suggest:

• easy to use
• not complicated
• basic in design or function

So it overlaps a lot with English simple, but context tells you the exact nuance.

Because gráficos is a thing, not a specific person.

Spanish uses the personal a mainly before a direct object that is a person (or sometimes a pet/personified being):

• Veo a la profesora. = I see the teacher.
• Conozco a Juan. = I know Juan.

But with things, there is normally no a:

• mostrar gráficos
• usar un programa

So gráficos does not take the personal a here.