La differenza è importante.

Italian often uses the definite article more than English does.
Here, la differenza means the difference.

So:

• la = the
• differenza = difference

In many contexts, Italian prefers the article where English might sometimes omit it or phrase things differently.

Yes. Differenza is a feminine singular noun, so it takes the feminine singular article la.

A quick breakdown:

• il = masculine singular
• la = feminine singular

Since differenza is feminine, you say:

• la differenza

not:

• il differenza

The accent is very important here. È with an accent means is.

So:

• è = is
• e = and

That means:

• La differenza è importante. = The difference is important.
• La differenza e importante. would be incorrect spelling in this sentence.

Importante is an adjective, and many Italian adjectives ending in -e have the same form for both masculine and feminine singular.

So you get:

• il libro è importante
• la differenza è importante

Both use importante.

Only the plural changes:

• i libri sono importanti
• le differenze sono importanti

In this sentence, importante is not directly modifying the noun inside the noun phrase. It comes after è because it is part of the predicate:

• La differenza = the subject
• è = is
• importante = important

This is the normal equivalent of English The difference is important.

If you put the adjective directly before or after the noun without è, you would be making a different structure, such as:

• la differenza importante = the important difference

That does not mean the difference is important.

Normally, no. In standard Italian, you would usually need the article here:

• La differenza è importante.

Leaving out la sounds incomplete or unnatural in an ordinary sentence.

Italian generally requires an article with singular countable nouns in cases like this.

Yes, you can say È importante la differenza, but it changes the emphasis.

• La differenza è importante. = neutral, standard word order
• È importante la differenza. = puts more focus on important or on the difference as the key element

The first version is the safest and most neutral for learners.

A helpful approximate pronunciation is:

deeff-eh-REN-tsa

A few details:

• di sounds like dee
• ff is a doubled consonant, so it is held a bit longer than a single f
• -enza is pronounced with a ts sound: -EN-tsa

The stress is on ren:

• dif-fe-REN-za

Italian usually does not need subject pronouns when the subject is already clear.

Here, the subject is explicitly stated:

• La differenza = the difference

So there is no need for a separate word like English it.

Italian says:

• La differenza è importante.

not something like:

• La differenza essa è importante. (unnatural/wrong here)

The plural would be:

• Le differenze sono importanti. = The differences are important.

Here is what changes:

• la → le
• differenza → differenze
• è → sono
• importante → importanti

Everything agrees in number.

Usually it matches English important very closely. It can mean:

• important
• significant
• meaningful in importance

So La differenza è importante can mean not only The difference is important, but in context also something like The difference matters.

That kind of nuance is very common in both languages.