Echipa este competitivă.

Because -a at the end is the definite article attached to the noun.

• echipă = a team
• echipa = the team

Romanian usually puts the definite article at the end of the noun, unlike English, which uses a separate word (the).

So:

• Echipă este competitivă would be wrong here
• Echipa este competitivă = The team is competitive

Yes. Echipă is a feminine singular noun.

That matters because adjectives in Romanian often change form to match the noun’s gender and number. Since echipa is feminine singular, the adjective also appears in the feminine singular form:

• masculine singular: competitiv
• feminine singular: competitivă

So echipa ... competitivă is correct agreement.

Because the adjective has to agree with echipa.

Here the noun is:

• feminine
• singular
• definite

The adjective matches the gender and number of the noun, so you get:

• un sport competitiv = a competitive sport
  (sport is masculine singular)
• o echipă competitivă = a competitive team
  (echipă is feminine singular)

So in your sentence, competitivă is the correct form.

Este means is. It is the 3rd person singular form of the verb a fi (to be).

In this sentence:

• Echipa = the team
• este = is
• competitivă = competitive

So the structure is very similar to English: subject + is + adjective.

In standard Romanian, este is normal and correct here. In casual speech, people very often use the shorter form e:

• Echipa este competitivă.
• Echipa e competitivă.

Both mean the same thing. Este is a bit more formal or careful; e is very common in everyday speech.

Normally, no in standard Romanian. You usually need the verb a fi in the present tense.

So:

• Echipa este competitivă. = correct
• Echipa competitivă. = not a normal complete sentence in this meaning

Without este, echipa competitivă would sound more like a noun phrase, meaning something like the competitive team, not the team is competitive.

The normal, neutral word order is:

• Echipa este competitivă.

Romanian does allow some flexibility in word order for emphasis or style. For example:

• Competitivă este echipa.

This is grammatically possible, but it sounds marked or literary, as if you are emphasizing competitive.

For everyday speech, stick with:

• Echipa este competitivă.

The letter ă is a very common Romanian vowel. It is a short, central vowel, similar to the a sound in English sofa for many speakers.

So roughly:

• echipă ≈ eh-KEE-puh
• competitivă ≈ kom-peh-tee-TEE-vuh

That final ă is not a full English a sound like in cat or day. It is weaker and more central.

The main stress is usually:

• echípă
• competitívă

So the sentence is pronounced roughly like:

• eh-KEE-puh ES-te kom-peh-tee-TEE-vuh

And in natural speech, if you use e instead of este, it may sound more like:

• eh-KEE-puh e kom-peh-tee-TEE-vuh

Because Romanian usually expresses the by attaching it to the noun as a suffix.

Compare:

• echipă = a team
• echipa = the team

This is one of the most important differences from English. Instead of putting the before the noun, Romanian often adds it to the end.

A few more examples:

• băiat = boy
• băiatul = the boy
• fată = girl
• fata = the girl

Yes, the sentence naturally describes a quality of the team: the team is competitive.

Romanian uses the adjective directly after este, just as English does:

• Echipa este competitivă.

If you wanted to make it more obviously about being one of the competitive teams, Romanian could use other structures, but for normal use this sentence simply means the team has that characteristic.

The indefinite version would be:

• O echipă este competitivă. = A team is competitive.

Here:

• o = a
• echipă = team
• este = is
• competitivă = competitive

Compare:

• O echipă este competitivă. = A team is competitive.
• Echipa este competitivă. = The team is competitive.

The plural would be:

• Echipele sunt competitive. = The teams are competitive.

Breakdown:

• echipele = the teams
• sunt = are
• competitive = feminine plural form of the adjective

So you can see both the noun and adjective change in the plural, and the verb changes from este to sunt.