Internet je dobrý zdroj informací.

It breaks down like this:

• Internet = the subject
• je = is (3rd person singular of být, to be)
• dobrý zdroj informací = the predicate noun phrase, meaning a good source of information

Inside that phrase:

• dobrý = good
• zdroj = source
• informací = of information

So the sentence is built very much like English: X is Y.

Because Czech does not have articles.

So where English says:

• the Internet
• a good source
• the source

Czech simply uses the noun without any article:

• Internet
• dobrý zdroj

Whether something means a, the, or just a general noun is understood from context.

In a normal full sentence like this, je is needed.

Czech usually keeps the present-tense form of být in sentences like:

• Internet je dobrý zdroj informací.
• To je problém.
• Praha je krásná.

Leaving it out would sound incomplete in ordinary standard Czech, though you may sometimes see omission in headlines, notes, or very compressed styles.

Because dobrý is an adjective modifying zdroj, and it must agree with zdroj in:

• gender
• number
• case

Here, zdroj is:

• masculine
• singular
• nominative

So the adjective is also masculine singular nominative: dobrý.

A useful point: dobrý agrees with zdroj, not with Internet directly. In this sentence, that is a little hidden because both Internet and zdroj are masculine singular. But you can see it more clearly in a sentence like:

• Wikipedia je dobrý zdroj informací.

Here Wikipedia is feminine, but dobrý still stays masculine, because it goes with zdroj.

That is a very common learner question.

After být (to be), Czech can use either:

• the nominative: je dobrý zdroj
• or the instrumental: je dobrým zdrojem

In this sentence, dobrý zdroj is in the nominative, which is completely natural.

The version with instrumental, Internet je dobrým zdrojem informací, is also possible. It can sound a bit more formal, more literary, or slightly more focused on the role/function of the Internet.

So:

• Internet je dobrý zdroj informací. = very natural
• Internet je dobrým zdrojem informací. = also correct

Because zdroj normally takes the genitive to express source of something.

In Czech you can ask:

• zdroj čeho? = a source of what?

Answer:

• informací

So informací is the genitive plural form of informace.

This is the normal pattern:

• zdroj informací = source of information
• nedostatek času = lack of time
• sklenice vody = glass of water

Because Czech often uses informace in the plural when talking about information in a general sense.

So English:

• a source of information

very naturally becomes Czech:

• zdroj informací

This is idiomatic Czech.

Using the singular informace here would suggest one specific piece or item of information, and zdroj informace would sound unusual in most general contexts.

Yes. Czech word order is much more flexible than English word order.

The sentence as given:

• Internet je dobrý zdroj informací.

is the most neutral order.

But other orders are possible, for example:

• Dobrý zdroj informací je internet.
• Internet je zdroj informací.
• Zdrojem informací je internet.

These versions can change emphasis, topic, or style, but the basic meaning can stay similar.

So the given word order is simply the most straightforward, neutral one.

Yes, internet / Internet is normally treated as a masculine inanimate noun in Czech.

As for capitalization, both spellings can be seen:

• Internet
• internet

In modern usage, lowercase internet is very common, especially when the word is treated as a general common noun. Uppercase Internet is also used, especially in older usage or styles that treat it more like a proper name.

So the sentence with Internet is fine, but you may also encounter:

• Internet je dobrý zdroj informací.
• Internet je dobrým zdrojem informací.
• internet je dobrý zdroj informací.

depending on style and editorial preference.