Územní platnost je v potvrzení o pojištění.

• územní = adjective, territorial / area-related
• platnost = noun, validity
• je = verb, 3rd person singular of být (to be)
• v = preposition, usually in
• potvrzení = noun, confirmation / certificate
• o = preposition, here roughly about / concerning
• pojištění = noun, insurance

So the basic structure is:

• Územní platnost = the subject
• je = the verb
• v potvrzení o pojištění = a prepositional phrase saying where that information is

Územní is an adjective of the soft adjective type. It modifies platnost, which is a feminine singular noun.

Because platnost is:

• feminine
• singular
• nominative

the adjective also appears in the matching form:

• územní platnost

This is normal agreement in Czech: adjectives usually match the noun in gender, number, and case.

Compare:

• územní platnost = territorial validity
• územního rozsahu = of territorial scope
• územním omezením = by territorial limitation

So here územní is simply the correct nominative singular feminine form.

A very useful clue is the ending -ost. Nouns ending in -ost are very often feminine in Czech.

Examples:

• platnost = validity
• možnost = possibility
• rychlost = speed
• společnost = company / society

That is why you say:

• ta platnost
  and why the verb is:
• platnost je = validity is

Je is the 3rd person singular form of být (to be).

Since the subject územní platnost is singular, Czech uses singular je:

• Územní platnost je... = Territorial validity is...

If the subject were plural, you would use jsou:

• Podmínky jsou v potvrzení. = The conditions are in the certificate.

So je is there simply because the subject is singular.

Because v normally requires the locative case when it means in.

The noun potvrzení is a neuter noun ending in -í, and in the singular its nominative and locative forms are often identical:

• nominative: potvrzení
• locative: v potvrzení

So even though the form looks unchanged, it is still locative after v.

This is common with many neuter nouns of this type:

• náměstí → na náměstí
• pojištění → v pojištění
• potvrzení → v potvrzení

Literally, it is confirmation/certificate about insurance, but in natural English it is usually something like:

• insurance certificate
• certificate of insurance
• proof of insurance

Czech often uses o + locative after nouns like potvrzení to show what the document concerns.

So:

• potvrzení o pojištění = a certificate concerning insurance

This is more idiomatic in Czech than trying to copy the English structure word-for-word.

The preposition o often takes the locative case and can mean about / concerning.

Here it tells you what the certificate is about:

• potvrzení o pojištění = certificate about insurance

The noun pojištění is in the locative after o, but its form happens to stay pojištění, just like potvrzení after v.

So:

• o pojištění is grammatically normal
• it does not mean someone is literally talking about insurance here
• it means the document concerns insurance

Because Czech has no articles like English a / an / the.

So:

• Územní platnost can mean territorial validity, the territorial validity, or sometimes just validity by territory/area, depending on context.
• v potvrzení o pojištění can mean in the insurance certificate or in an insurance certificate, again depending on context.

Czech relies on context much more than English for definiteness.

It is understandable, but it feels a bit formal and compressed, like language from a form, website, or official instructions.

A more natural full sentence might be:

• Územní platnost je uvedena v potvrzení o pojištění.
  = The territorial validity is stated in the insurance certificate.

Or:

• Územní platnost najdete v potvrzení o pojištění.
  = You can find the territorial validity in the insurance certificate.

So the original sentence is not wrong, but it sounds somewhat elliptical, as official Czech often does.

Yes, Czech word order is fairly flexible.

The neutral order here is:

• Územní platnost je v potvrzení o pojištění.

But other orders are possible depending on emphasis:

• V potvrzení o pojištění je územní platnost.
• V potvrzení o pojištění je uvedena územní platnost.

Czech often puts known information earlier and new or emphasized information later. In a practical context, starting with Územní platnost makes sense because that is probably the topic being discussed.

They are both neuter nouns, but they come from different bases:

• potvrzení comes from potvrdit = to confirm
  → potvrzení = confirmation / certificate

• pojištění comes from pojistit = to insure
  → pojištění = insurance / insuring

Both are very common examples of verbal nouns in Czech. English often translates them with abstract nouns ending in -tion, -ment, or just a different noun altogether.

So even though they look structurally similar, they mean different things:

• potvrzení = the document or act of confirming
• pojištění = insurance

A rough English-friendly pronunciation is:

OO-zem-nee PLAT-nost yeh f pot-vr-zeh-nyee o poy-ish-tyeh-nyee

A few useful details:

• ú = long oo
• ž sounds like the s in measure
• š sounds like sh
• ř is a special Czech sound; in potvrzení you do not have ř, only r
• ě often softens the preceding consonant
• v is often pronounced more like f before a voiceless consonant, so v potvrzení sounds close to f potvrzení

You do not need perfect pronunciation right away, but it helps to notice that v changes its sound in connected speech.

Here are a few more explicit versions:

• Územní platnost je uvedena v potvrzení o pojištění.
  = The territorial validity is stated in the insurance certificate.

• Informaci o územní platnosti najdete v potvrzení o pojištění.
  = You will find information about territorial validity in the insurance certificate.

• Územní platnost je napsaná v potvrzení o pojištění.
  = The territorial validity is written in the insurance certificate.
  (more informal)

These are useful because the original sentence can feel slightly abbreviated. Adding uvedena, najdete, or napsaná makes the meaning more explicit for learners.