Tito lidé tvoří skupinu.

Tito is the nominative plural masculine animate form of tento, which means this / these.

Because lidé means people and is grammatically masculine animate plural, the demonstrative has to match it:

• tito lidé = these people

By contrast, tyto is used with many other plural nouns, but not with masculine animate nouns in the nominative:

• tyto knihy = these books
• tyto ženy = these women

So tito lidé is the correct agreement.

Lidé means people. Its singular is člověk, meaning person / human.

This is an irregular plural, so you cannot predict it just from the singular ending. You need to learn it as a pair:

• člověk = person
• lidé = people

Lidé is the standard nominative plural form, and here the word is the subject of the sentence, so lidé is the expected form in careful standard Czech.

Lidi is very common in everyday speech, but it is more colloquial. So:

• Tito lidé tvoří skupinu. = standard
• Tihle lidi tvoří skupinu. = common in informal speech

A learner should definitely recognize lidi, but lidé is the safer choice for standard Czech.

Lidé is in the nominative plural.

It is nominative because it is the subject of the sentence: these people are the ones doing the action of tvoří.

In other words:

• Who forms the group?
• Tito lidé.

That tells you it is the subject, so nominative is used.

Because skupinu is the accusative singular of skupina.

The noun skupina is the direct object of the verb tvoří. In Czech, direct objects often go in the accusative case.

So:

• skupina = nominative singular
• skupinu = accusative singular

Here the sentence is answering:

• What do these people form?
• A group.

That is why Czech uses skupinu.

Here tvoří means something like form, make up, or constitute.

The infinitive is tvořit.

Depending on context, tvořit can mean:

• to create
• to form
• to make up
• to constitute

In this sentence, the most natural sense is form / make up:

• These people form a group
• These people make up a group

That is just how this verb pattern works in Czech.

For tvořit, the present tense is:

• já tvořím
• ty tvoříš
• on/ona/ono tvoří
• my tvoříme
• vy tvoříte
• oni/ony tvoří

So the 3rd person singular and 3rd person plural are both tvoří.

You tell whether it means he/she/it forms or they form from the subject:

• On tvoří skupinu.
• Tito lidé tvoří skupinu.

It can mean either, depending on context.

Czech present tense often covers both:

• a general/habitual meaning: form
• an ongoing meaning: are forming

So tvoří does not force the same distinction that English does between form and are forming.

In this sentence, the most natural interpretation is probably form / make up / constitute, but context always matters.

Yes. Czech word order is much more flexible than English word order because the cases show the grammatical roles.

The sentence:

• Tito lidé tvoří skupinu.

is a neutral, straightforward order.

But you could also say:

• Skupinu tvoří tito lidé.

That still means the same basic thing, but it changes the focus or emphasis. This version puts more attention on skupinu first, as if answering Who makes up the group?

So the word order can change, but the choice affects style and emphasis.

Because Czech has no articles like English a and the.

So Czech simply says:

• tvoří skupinu

and the listener understands from context whether it is a group, the group, or just group in a broader sense.

This is very normal in Czech. You should not try to translate English articles word-for-word.

Yes, Tito lidé sounds standard and somewhat more careful or written.

In everyday spoken Czech, you will often hear more colloquial versions such as:

• Tihle lidi

That said:

• tito lidé = standard, good for writing and careful speech
• tihle lidi = very common in informal conversation

As a learner, it is useful to know both, but tito lidé is the better model to learn first.

Yes. It is a normal and natural way to say that several people form or make up a group.

It often has the sense of constituting a group rather than physically creating one from nothing.

So in this sentence, it does not necessarily mean they are actively building a group right now. It can simply mean that, taken together, they are a group or make up a group.