Babcia zawsze wkłada fartuch, kiedy piecze ciasto dla gości.

Babcia is the subject of the sentence, so it is in the nominative case. It means grandma / grandmother.

It comes first because that is the most neutral word order here: first the person, then the adverb, then the verb.

Also, Polish has no articles, so Babcia can mean Grandma, the grandmother, or just grandma, depending on context.

Zawsze means always. It tells us this is a habitual action, not just something happening once.

In this sentence, Babcia zawsze wkłada fartuch sounds very natural:
Grandma always puts on an apron...

Polish word order is flexible, so zawsze can move, but its position changes emphasis. This version is the most neutral and common.

Wkłada comes from wkładać, which can mean to put on clothing or to put in / insert, depending on context. With fartuch it clearly means put on an apron.

You may also hear zakładać fartuch. That is also possible. In everyday Polish, both can be used for putting on clothes, though the exact preference can depend on the item and speaker.

Here, wkłada fartuch is completely natural.

Because this sentence describes a repeated, usual action: Grandma always does this when she bakes.

• wkłada = imperfective, used for habits and ongoing/repeated actions
• włoży = perfective, used for a single completed future action

So:

• Babcia zawsze wkłada fartuch... = habitual, general truth
• Babcia włoży fartuch... = Grandma will put on an apron

Fartuch is the direct object of wkłada, so it is in the accusative case.

But fartuch is a masculine inanimate noun, and in the singular, masculine inanimate nouns usually have the same form in the accusative as in the nominative.

So:

• nominative: fartuch
• accusative: fartuch

That is why there is no visible change.

Piecze is the 3rd person singular present tense form of piec.

The verb changes its stem in the present tense:

• infinitive: piec = to bake
• ja: piekę
• ty: pieczesz
• on/ona: piecze

So Babcia piecze means Grandma bakes / is baking.

This kind of stem change is normal in Polish verbs.

Because Polish, like English, uses the present tense for habitual actions.

The sentence means something like:

Whenever Grandma bakes a cake for guests, she always puts on an apron.

So this is not about one specific moment. It is a general routine. The word zawsze strongly supports that reading.

Ciasto can mean cake, but it can also mean dough depending on context.

In this sentence, because Grandma is baking it for guests, the most natural meaning is cake or possibly a baked sweet dish / pastry.

So learners should remember that ciasto is a broader word than English cake in some contexts.

Because Polish often uses the singular when talking about one baked item, or sometimes something treated as one whole thing.

Here, piecze ciasto most naturally means she bakes a cake.

If you wanted to talk about several cakes, you would use the plural, for example piecze ciasta.

The preposition dla means for, and it always takes the genitive case.

So:

• basic form: gość = guest
• nominative plural: goście = guests
• genitive plural after dla: gości

That is why we get dla gości = for guests / for the guests.

Because kiedy piecze ciasto dla gości is a subordinate clause.

In Polish, subordinate clauses introduced by words like kiedy, że, bo, jeśli, and others are normally separated by a comma.

So the comma here is required: Babcia zawsze wkłada fartuch, kiedy piecze ciasto dla gości.

Yes. Kiedy and gdy can both mean when in sentences like this.

So you could also say:

Babcia zawsze wkłada fartuch, gdy piecze ciasto dla gości.

Both are correct.
Kiedy is very common and neutral.
Gdy can sound a little more literary or formal in some contexts, but it is still very normal.

Yes. Polish word order is flexible because case endings show grammatical roles.

This version is the most neutral:

Babcia zawsze wkłada fartuch, kiedy piecze ciasto dla gości.

But other orders are possible for emphasis, for example:

• Zawsze babcia wkłada fartuch, kiedy piecze ciasto dla gości.
  This puts more stress on always.

• Kiedy piecze ciasto dla gości, babcia zawsze wkłada fartuch.
  This foregrounds the when clause.

The meaning stays similar, but the focus changes.

A rough English-friendly guide:

• Babcia ≈ BAHP-chya
• wkłada ≈ FKWA-da or VKWA-da depending on speed/region
• fartuch ≈ FAR-toohkh
• piecze ≈ PYE-che
• ciasto ≈ CHAS-to
• gości ≈ GOSH-chee

A few useful sound notes:

• ci before a vowel often sounds like a soft ch / ć sound
• cz sounds like English ch but harder
• ś is a soft sh sound
• ł sounds like English w