Na desáté stránce je krátký text o rodině.

In Czech, na stránce is the normal way to say on a page.

• na often means on
• with location, na usually takes the locative case

So:

• na stránce = on the page
• na desáté stránce = on the tenth page

This matches English quite closely: we also usually say on page ten or on the tenth page.

Because desáté describes stránce, and both words must match in:

• gender
• number
• case

Here, stránka is:

• feminine
• singular
• in the locative case because it follows na in a location expression

So the ordinal desátý changes to the feminine singular locative form:

• desátý → desáté

And stránka changes to its locative singular form:

• stránka → stránce

So:

• na desáté stránce = on the tenth page

This is a normal case ending change.

The dictionary form is:

• stránka = page

But after na when it means location, Czech uses the locative singular.

For many feminine nouns ending in -ka, the locative singular often changes like this:

• -ka → -ce

So:

• stránka → stránce

Other nouns can behave similarly, though you should learn each pattern gradually rather than assuming they all work exactly the same way.

Because the sentence has a singular subject.

The key noun is:

• text = text

Since text is singular, the verb is also singular:

• je = is

If there were more than one text, you would use:

• jsou = are

For example:

• Na desáté stránce jsou krátké texty o rodině.
• On the tenth page there are short texts about family.

Because krátký has to agree with text.

The noun text is:

• masculine inanimate
• singular
• here in the nominative

So the adjective also takes the matching form:

• krátký text = a short text

This is the basic nominative singular masculine inanimate form of the adjective.

Compare:

• krátký text — masculine singular
• krátká kniha — feminine singular
• krátké slovo — neuter singular
• krátké texty — plural

Because the preposition o meaning about requires the locative case.

The basic form is:

• rodina = family

After o, it changes to:

• rodině

So:

• o rodině = about family / about the family

This is a very common pattern:

• o škole = about school
• o městě = about the city
• o učiteli = about the teacher

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

So krátký text can mean:

• a short text
• the short text

The exact meaning depends on context.

In this sentence, English will usually translate it as:

• On the tenth page there is a short text about family.

because that sounds most natural if the text is being mentioned for the first time.

Czech word order is more flexible than English word order.

Starting with Na desáté stránce puts the location first:

• Na desáté stránce je krátký text o rodině.

This is very natural if you are telling someone where something is.

You could also say:

• Krátký text o rodině je na desáté stránce.

That is also grammatical, but it sounds a bit more like you are talking about the short text first and then saying where it is.

So the original sentence is a very normal way to present new information: On the tenth page, there is a short text about family.

It is the normal verb být = to be, but in this sentence it functions like English there is.

So:

• je krátký text literally looks like is a short text
• but natural English is there is a short text

This is very common in Czech. Czech often does not need a separate word for English there in there is / there are sentences.

So:

• Na desáté stránce je krátký text o rodině.
• natural English: There is a short text about family on the tenth page.

A rough pronunciation guide is:

• na deh-ZAA-teh STRAAN-tseh yeh KRAAT-kee tekst o ROH-dih-nyeh

A few useful points:

• á is a long vowel, so desáté and krátký have longer vowel sounds
• stránce ends with -ce, pronounced roughly like tseh
• je sounds like yeh
• dě / tě / ně-type combinations often sound softer; rodině ends roughly -nyeh

If you want, a very careful word-by-word breakdown is:

• Na = nah
• desáté = deh-ZAA-teh
• stránce = STRAAN-tseh
• je = yeh
• krátký = KRAAT-kee
• text = tekst
• o = oh
• rodině = ROH-dih-nyeh

Not in the same way.

In Czech, page numbers are often expressed with an ordinal adjective when you say on the tenth page:

• na desáté stránce

You may also hear structures like:

• na straně deset = on page ten

That uses strana in a different form and the cardinal number deset.

So both types exist, but they are not built the same way:

• na desáté stránce = on the tenth page
• na straně deset = on page ten

The sentence you were given uses the ordinal-style expression, which is completely natural.