La profesora nos explicó que el tiempo del verbo cambia, pero el pronombre no.

In Spanish, it is very normal to use the definite article with a specific person’s role or profession.

So la profesora means the teacher or the female teacher.

Compare:

• La profesora nos explicó... = The teacher explained to us...
• Profesora by itself would usually be used when directly addressing her, like Profesora, tengo una duda. = Teacher, I have a question.

Yes, profesora means female teacher.

Spanish often marks gender in nouns referring to people:

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

In English, teacher does not usually show gender, but in Spanish it often does.

Nos means us or to us.

In this sentence, it is the indirect object pronoun, so the idea is:

• La profesora nos explicó...
• literally: The teacher explained to us...

In natural English, we usually say The teacher explained to us that... or simply The teacher explained that...

Because object pronouns like me, te, nos, le, lo, la usually go before a conjugated verb in Spanish.

So:

• nos explicó = explained to us
• me dijo = told me
• te llamó = called you

Spanish does not normally say explicó nos with a finite verb.

Pronouns are attached to the end only in certain cases, such as:

• infinitives: explicarnos
• gerunds: explicándonos
• affirmative commands: explícanos

Explicó is the preterite, which is commonly used for a completed action in the past.

So here it means that the teacher explained it at a particular moment or as a completed event.

• explicó = explained
• explicaba = was explaining / used to explain

If you say:

• La profesora nos explicó...
  it sounds like one completed explanation.

If you say:

• La profesora nos explicaba...
  it sounds more like background, an ongoing explanation, or something habitual.

Que here means that and introduces the clause that follows the verb explicó.

So:

• nos explicó que... = explained to us that...

This is very common in Spanish after verbs like:

• decir que = to say that
• explicar que = to explain that
• creer que = to believe that
• pensar que = to think that

Unlike in English, where that is often omitted, Spanish usually keeps que.

Yes. In grammar, tiempo means tense.

So:

• el tiempo del verbo = the tense of the verb

Even though tiempo often means time in everyday language, in grammar it is also used for tense.

Examples:

• tiempo presente = present tense
• tiempo pasado = past tense

Because the teacher explained a general rule, and Spanish often uses the present tense for things that are generally true.

So the sentence means:

• the act of explaining happened in the past: explicó
• the rule itself is still presented as true now: cambia

This is very natural in both Spanish and English:

• She explained that the verb tense changes...

You could think of it as: she explained a rule, and the rule is still valid.

Because Spanish often leaves out repeated words when they are already understood from the context.

Here, no stands for no cambia.

So:

• el tiempo del verbo cambia, pero el pronombre no
• literally: the verb tense changes, but the pronoun does not

This is called ellipsis: the repeated verb is omitted because it would be redundant.

A full version would be:

• La profesora nos explicó que el tiempo del verbo cambia, pero el pronombre no cambia.

But the shorter version sounds more natural.

Because these are specific nouns being talked about in a general grammatical statement:

• el tiempo del verbo = the tense of the verb
• el pronombre = the pronoun

Spanish uses articles more often than English does. In grammar explanations, this is very common.

Also, the articles match the gender of the nouns:

• el tiempo — masculine
• el verbo — masculine
• el pronombre — masculine

Because de + el contracts to del in Spanish.

So:

• de + el verbo → del verbo

This contraction is mandatory.

Compare:

• el tiempo del verbo
• la explicación del profesor

But note that de + la does not contract:

• de la profesora = not contracted

Yes, pronombre is masculine: el pronombre.

Nouns ending in -e can be either masculine or feminine, so you often just have to learn the article with the noun.

For example:

• el pronombre = the pronoun
• la clase = the class
• el estudiante / la estudiante = depends on the person

A good habit is to learn nouns together with their article:

• el pronombre
• el verbo
• la profesora

No, not in normal English.

Spanish explicar can take an indirect object pronoun like nos, but in English we usually say:

• explained to us
• or simply explained

So:

• La profesora nos explicó que...
  = The teacher explained to us that...

not The teacher explained us that...

This is a good example of where Spanish and English structure the verb differently.

The sentence has two main parts:

1. La profesora nos explicó
   = main clause
   = The teacher explained to us

2. que el tiempo del verbo cambia, pero el pronombre no
   = subordinate clause introduced by que
   = that the verb tense changes, but the pronoun does not

Inside that second part, there is a contrast:

• el tiempo del verbo cambia = the verb tense changes
• pero el pronombre no = but the pronoun does not

So the sentence is built very logically:

• someone explained something
• and what was explained was a contrast between two grammatical elements