Rezervna kopija će zaštititi korisničke podatke.

Će is the future-tense auxiliary, so it corresponds to will in English.

So:

Rezervna kopija će zaštititi korisničke podatke.
= A/The backup copy will protect user data.

In Serbian, the main verb often stays in the infinitive after this auxiliary, so će zaštititi = will protect.

Because će is a clitic, and Serbian clitics normally go in the second position of the sentence or clause.

Here the first unit is Rezervna kopija, so the clitic comes right after it:

Rezervna kopija | će | zaštititi korisničke podatke.

That word order is very natural and neutral in Serbian.

This is about aspect, which is very important in Serbian.

• zaštititi = perfective
  focuses on a completed result: to protect successfully / to provide protection
• štititi = imperfective
  focuses on an ongoing or repeated action: to be protecting / to protect regularly

In this sentence, the idea is that the backup will accomplish the protective result, so zaštititi is the natural choice.

Rezervna kopija is nominative singular feminine, because it is the subject of the sentence.

• kopija = copy, feminine singular
• rezervna = backup/reserve, agreeing with kopija

So the adjective and noun match:

• feminine
• singular
• nominative

If it were a direct object instead, you would expect different forms, for example rezervnu kopiju.

Serbian often uses an adjective where English uses a noun modifier.

So instead of something literally like user data, Serbian commonly says:

• korisnik = user
• korisnički = user-related, user, user's

That means:

• korisnički podaci = user data

So korisničke is not a separate noun meaning user. It is an adjective derived from korisnik and used to describe the noun podatke.

Because this phrase is the direct object of the verb zaštititi, so it must be in the accusative plural.

Base form:

• korisnički podaci = user data, nominative plural

Object form:

• korisničke podatke = user data, accusative plural

Both words change because the adjective must agree with the noun in:

• gender
• number
• case

So:

• nominative plural: korisnički podaci
• accusative plural: korisničke podatke

It is plural.

The singular is:

• podatak = a datum / a piece of data

The plural is:

• podaci = data
• podatke = data in the accusative plural

In Serbian, data is very often expressed with a normal plural noun, so using a plural form here is completely natural.

Yes. Rezervna kopija is a very normal and standard way to say backup copy or simply backup, especially in software, help text, and formal language.

Literally it means:

• rezervna = reserve / backup
• kopija = copy

You may also hear bekap in informal IT speech, but rezervna kopija is the more standard Serbian expression.

Yes, Serbian word order is fairly flexible because case endings show who is doing what.

The neutral order here is:

Rezervna kopija će zaštititi korisničke podatke.

But you could also move things for emphasis, for example:

Korisničke podatke će zaštititi rezervna kopija.

That puts more focus on the user data.

What usually stays true, though, is that the clitic će still tends to appear in the second position.

Because Serbian has no articles.

So rezervna kopija can mean:

• a backup copy
• the backup copy

And korisničke podatke can mean:

• user data
• the user data
• users' data

The exact meaning depends on context, not on an article word like in English.