La macchia sul tavolo è ancora visibile.

Because macchia is a feminine singular noun in Italian, so it takes the feminine singular article la.

• la macchia = the stain / the spot
• il is used with masculine singular nouns, so it would be wrong here.

A useful habit in Italian is to learn nouns together with their article:

• la macchia
• il tavolo

In Italian, c before i or e is normally pronounced like English ch.
So if Italian wrote macia, it would sound wrong.

The spelling ch keeps the hard k sound:

• macchia = pronounced roughly MAK-kya
• compare:
  • ce / ci = soft sound
  • che / chi = hard sound

So the h is there to preserve the hard pronunciation of c before i.

Sul means on the.

It is a contraction of:

• su = on
• il = the

So:

• su + il = sul

This kind of contraction is very common in Italian with prepositions + articles:

• su + il = sul
• su + la = sulla
• su + i = sui
• su + gli = sugli
• su + le = sulle

So sul tavolo literally means on the table.

Both can mean on the table, but they are used a little differently.

• sul tavolo is the most natural, ordinary way to say on the table
• sopra il tavolo is also correct, but it can sound a bit more explicit, like above/on top of the table

In many everyday contexts, Italians prefer su + article:

• sul tavolo
• sulla sedia
• sul letto

So in this sentence, sul tavolo is the most normal choice.

The accent distinguishes è (is) from e (and).

• è = is
• e = and

So:

• La macchia sul tavolo è ancora visibile. = The stain on the table is still visible.
• Without the accent, it would be a different word and incorrect here.

This is a very important spelling point in Italian.

Ancora is an adverb meaning still (or sometimes again, depending on context).
Here it modifies the adjective visibile, so è ancora visibile means is still visible.

This word order is very natural in Italian:

• è ancora visibile
• è ancora aperto
• è ancora qui

You may sometimes see adverbs in slightly different positions, but in this sentence ancora before visibile is the normal choice.

Yes, it does agree with macchia, but visibile belongs to a class of adjectives that have the same form for masculine and feminine singular.

So:

• il segno è visibile
• la macchia è visibile

For the plural, it changes to:

• i segni sono visibili
• le macchie sono visibili

So the agreement is there, but the singular masculine and feminine happen to look the same.

Because sul tavolo means the stain is located on the table.

• sul tavolo = on the table
• del tavolo = of the table

So:

• La macchia sul tavolo = the stain on the table
• La macchia del tavolo would suggest something like the table’s stain, which is usually not what you mean.

Italian often uses a prepositional phrase after the noun, just like English does.

Yes, a little.

The original sentence:

• La macchia sul tavolo è ancora visibile.

is the most neutral and natural version.

You could also say:

• La macchia è ancora visibile sul tavolo.

This is grammatically possible, but it may sound as if you are focusing more on where it is visible.

So the original order is usually better if sul tavolo simply identifies which stain you mean.

Yes. That would be a natural alternative, but the structure is different.

• La macchia sul tavolo è ancora visibile.
  = The stain on the table is still visible.
• Si vede ancora la macchia sul tavolo.
  = You can still see the stain on the table. / The stain on the table is still visible.

The original sentence is more descriptive and a bit more formal or neutral.
The si vede version is often more conversational.

A simple pronunciation guide is:

La MAK-kya sul TA-vo-lo eh an-KO-ra vee-ZEE-bee-leh.

A few key points:

• macchia = MAK-kya
• tavolo = TA-vo-lo
• è = eh
• ancora = an-KO-ra
• visibile = vee-ZEE-bee-leh

Italian pronunciation is usually quite regular, so once you learn the spelling rules, it becomes much easier to read aloud.