El líder explicó el cambio.

They are doing two different jobs:

• El líder = the leader → here el is the definite article for the subject.
• el cambio = the change → here el is the definite article for the direct object.

Spanish often uses articles more consistently than English, so having el ... el ... in the same sentence is completely normal.

Explicó is the preterite tense, third person singular, of explicar.

So it means:

• he explained
• she explained
• it explained (less likely here)
• or the leader explained

The preterite is used for a completed action in the past.

The accent mark shows where the stress goes: ex-pli-CÓ.

It also helps distinguish this form from explico, which means I explain or I am explaining in some contexts.

So:

• explico = I explain
• explicó = he/she explained

That written accent is very important.

Líder is stressed on the first syllable: LÍ-der.

The accent mark shows that pronunciation clearly. Without it, the stress rules of Spanish would suggest a different pattern. So the written accent tells you the word is pronounced correctly and should be stressed on lí.

Because el cambio is a thing, not a person.

Spanish uses the personal a before a specific human direct object, and sometimes pets or personified beings. But with things, you normally do not use it.

So:

• El líder explicó el cambio = correct
• not El líder explicó a el cambio

You would see a with a person, for example:

• El líder explicó el cambio a los empleados = The leader explained the change to the employees

There, a los empleados means to the employees, not the personal a for a direct object.

Yes. El cambio is the direct object because it is the thing being explained.

A useful question is: What did the leader explain? Answer: the change.

So the structure is:

• El líder = subject
• explicó = verb
• el cambio = direct object

No, not naturally.

Explicó is preterite, so it expresses a finished past action: explained.

If you wanted was explaining, Spanish would normally use the imperfect or a progressive form, such as:

• El líder explicaba el cambio = The leader was explaining the change / used to explain the change
• El líder estaba explicando el cambio = The leader was explaining the change

So explicó points to a completed event.

This is the most neutral and common Spanish word order:

• Subject + Verb + Object

So:

• El líder = subject
• explicó = verb
• el cambio = object

Spanish can change word order more easily than English for emphasis or style, but this version is the standard, straightforward one.

A broad Spain pronunciation would be approximately:

el LEE-der eks-plee-KOH el KAM-byo

A few details:

• líder → stress on lí
• explicó → stress on the last syllable -có
• cambio → cam-byo
• the c in cambio is a hard k sound because it comes before a
• the x in explicó sounds like ks

A more IPA-style version would be roughly:

[el ˈliðeɾ ekspliˈko el ˈkambjo]

In much of Spain, the d in líder may sound softer between vowels.

Yes, it can.

In modern Spanish, líder is often used for both men and women. The article usually shows the gender:

• el líder = the male leader
• la líder = the female leader

So if the leader were a woman, you could say:

• La líder explicó el cambio

Because cambio is a noun and cambiar is a verb.

• cambio = change
• cambiar = to change

In this sentence, the verb is already explicó, so after it we need the thing that was explained: el cambio.

So:

• explicó el cambio = explained the change

not

• explicó cambiar

because that would mean something different and would not fit this sentence.

Yes. You can explain something to someone.

This sentence only includes the thing explained:

• El líder explicó el cambio = The leader explained the change

But you can add the person receiving the explanation:

• El líder explicó el cambio a los empleados = The leader explained the change to the employees

So explicar commonly works like this:

• explicar algo = explain something
• explicar algo a alguien = explain something to someone