Guardo las llaves en el cajón de mi escritorio.

Because Spanish often drops subject pronouns when they are not needed.

The verb guardo already tells you the subject is I, because it is the first-person singular form of guardar.

So:

• Guardo las llaves... = I keep / I store / I put away the keys...
• Yo guardo las llaves... = also correct, but yo is only added for emphasis, contrast, or clarity.

For example:

• Yo guardo las llaves, no tú. = I keep the keys, not you.

In a neutral sentence, leaving out yo is the most natural choice.

Here, guardo comes from guardar, which often means:

• to keep
• to store
• to put away
• sometimes to save

In this sentence, guardo las llaves en el cajón de mi escritorio, the most natural meaning is something like:

• I keep the keys in my desk drawer
• I put the keys away in my desk drawer

So guardar is not just about physically placing something somewhere once; it can also suggest that this is where you normally keep it.

Spanish uses the definite article much more often than English does.

So las llaves literally means the keys, but in English we might simply say I keep my keys in my desk drawer or I keep the keys in my desk drawer, depending on context.

Here, las llaves suggests specific keys that are understood in the situation.

Compare:

• Guardo las llaves... = I keep the keys... / I keep my keys... depending on context
• Guardo unas llaves... = I keep some keys...
• Guardo mis llaves... = I keep my keys... with explicit possession

So las llaves is completely natural even where English might prefer my keys.

Yes, absolutely.

• Guardo las llaves en el cajón de mi escritorio.
• Guardo mis llaves en el cajón de mi escritorio.

Both are correct, but the nuance is slightly different:

• las llaves = the keys, or keys understood from context
• mis llaves = my keys, explicitly stating possession

Spanish often uses the article where English would use a possessive, especially when the owner is obvious from context. But with ordinary objects like keys, mis llaves is also very common.

En is the normal preposition for in, inside, or at, depending on context.

Here:

• en el cajón = in the drawer

And el is the definite article the.

So:

• en = in
• el cajón = the drawer

Together: in the drawer

Spanish normally includes the article with nouns like this, so en el cajón is the expected structure.

Because el cajón means the drawer, referring to a specific drawer that is identifiable.

• en el cajón = in the drawer
• en un cajón = in a drawer

In your sentence, the drawer is made specific by the rest of the phrase:

• el cajón de mi escritorio = the drawer of my desk / my desk drawer

So it is not just any drawer; it is a particular one.

Here, de means something like of or belonging to.

So:

• el cajón de mi escritorio = literally the drawer of my desk
• more natural English: the drawer of my desk or my desk drawer

This is a very common Spanish structure:

• la puerta de la casa = the door of the house / the house door
• el color del coche = the color of the car
• el cajón de mi escritorio = the drawer of my desk

So de is linking the drawer to the desk.

Because in Spanish, possessive adjectives like mi, tu, su, nuestro usually replace the article.

So you say:

• mi escritorio = my desk
• tu libro = your book
• su casa = his/her/your house

Not:

• el mi escritorio ❌

This is different from some older forms of Spanish or other languages, but in modern standard Spanish, mi already does the job of marking possession, so no article is used before it.

In this sentence, escritorio means desk.

That is an important point, because English speakers sometimes confuse it with office.

In Spanish (including Spain Spanish):

• escritorio = desk
• oficina = office
• despacho = office/study, especially a private office or study room

So:

• el cajón de mi escritorio = the drawer of my desk
• not the drawer of my office

Guardo is the present indicative form of guardar.

The Spanish present tense can cover several ideas that English expresses in different ways, depending on context:

• I keep
• I store
• I put away
• sometimes I am keeping

In this sentence, the most natural interpretation is usually a habitual or general present:

• I keep the keys in my desk drawer

But in the right context, it could also describe what someone is doing now:

• ¿Dónde pongo las llaves?
• Guardo las llaves en el cajón de mi escritorio.

So the exact English translation depends on context.

Cajón is pronounced roughly like ka-HON in Spain Spanish.

A few useful points:

• the j sounds like a strong throaty h
• the stress falls on the last syllable: -jón
• the accent mark tells you where the stress goes

Without the accent mark, cajon would follow the normal stress rules differently and would not be pronounced the same way.

So the written accent in cajón is important because it shows that the stress is on the final syllable.

Yes, you could.

• en el cajón = in the drawer
• dentro del cajón = inside the drawer

Both are correct, but en el cajón is the simpler and more natural everyday wording here.

Dentro de adds a bit more emphasis to the idea of being physically inside something. In most normal situations, Spanish speakers would probably just say en el cajón.

The given word order is the most neutral and natural one:

• Guardo las llaves en el cajón de mi escritorio.

Spanish word order is fairly flexible, but changing it usually changes the emphasis.

For example:

• Las llaves las guardo en el cajón de mi escritorio.
  This emphasizes the keys.
• En el cajón de mi escritorio guardo las llaves.
  This emphasizes where I keep them.

So yes, the word order can change, but the original version is the best basic model for a learner.