Las bases reguladoras explican la concurrencia competitiva.

Because base is a feminine noun in Spanish: la base.

So in the plural, it becomes las bases.
The adjective also has to agree in gender and number, so:

• la base reguladora
• las bases reguladoras

Spanish adjectives must match the noun they describe.

The singular is:

• la base reguladora

That gives you the pattern:

• la base reguladora
• las bases reguladoras

In Spanish, adjectives often come after the noun, especially when they are classifying the noun rather than adding a personal opinion or emphasis.

So:

• bases reguladoras = regulatory/governing rules/bases

This is the normal order in formal or administrative Spanish.
Putting the adjective before the noun would sound unusual here and could change the tone.

Because the subject is las bases reguladoras, which is third person plural.

The verb has to agree with the subject:

• la base reguladora explica
• las bases reguladoras explican

So explican means they explain.

Spanish often leaves out subject pronouns when they are not needed. The verb ending already tells you who the subject is.

Here, explican already shows a third-person plural subject, and the sentence clearly names that subject anyway:

• Las bases reguladoras explican...

So adding ellas would be unnecessary and unnatural in most contexts.

Spanish uses the definite article much more often than English, especially with:

• abstract ideas
• formal concepts
• legal or administrative terms

Here, la concurrencia competitiva is being treated as a specific concept or procedure, so the article sounds natural.

In this kind of formal Spanish, dropping la would usually sound wrong.

Yes, especially in Spanish administrative and legal language.

In Spain, concurrencia competitiva is a standard term often used for a process where applications or proposals are compared and awarded according to set criteria. It is common in things like:

• grants
• subsidies
• public calls
• official procedures

So even if the literal words may look strange to an English speaker, together they form a recognised formal expression.

It is an adjective.

It describes bases and agrees with it in:

• gender: feminine
• number: plural

So:

• bases = noun
• reguladoras = adjective describing that noun

Explican is a verb form, from the infinitive explicar.

In this sentence it is:

• present tense
• indicative mood
• third person plural

So it means they explain or explain depending on how you translate it in context.

No. Explicar normally takes a direct object with no preposition.

So:

• explicar algo = to explain something
• explican la concurrencia competitiva = they explain the competitive procedure/concept

You would not say explican de la concurrencia competitiva here.

This is the most neutral and standard Spanish word order:

• Subject: Las bases reguladoras
• Verb: explican
• Object: la concurrencia competitiva

Spanish can sometimes change word order for emphasis, but this sentence uses the default order and sounds natural, especially in formal writing.

Grammatically, it comes from the idea of regulating/governing, yes, but in real usage a more natural English translation often depends on context.

In official Spanish, bases reguladoras is a set phrase that often refers to the rules, governing terms, or regulatory framework for something like a grant or official process.

So while reguladoras is literally related to regulating, the best English wording is often less literal.

Yes, very much so.

Words like:

• bases reguladoras
• concurrencia competitiva

belong to a formal, administrative, or legal register.
A learner should recognise that this is not casual everyday conversation, but the kind of wording you might see in:

• official documents
• grant notices
• public administration texts
• regulations

Because it is the thing being explained.

In the sentence:

• Las bases reguladoras = the subject, the thing doing the action
• explican = the action
• la concurrencia competitiva = the direct object, what is being explained

A good test is to ask: What do the bases reguladoras explain?
Answer: la concurrencia competitiva.

You can, but it changes the meaning slightly.

• explican = explain / do explain / explain in general
• están explicando = are explaining right now

The original sentence sounds more neutral and general, which fits formal writing better.
The progressive form (están explicando) would suggest an ongoing action at this moment.

Yes. They are related.

• Spanish: base
• English: base, basis

In this sentence, though, bases does not necessarily mean physical bases. In formal Spanish it can mean things like:

• terms
• rules
• guidelines
• governing provisions

So the exact English equivalent depends on context.