Learn Hardcore Spanish (Spain): En la manifestación, una política joven explicó a la ciudadanía que cada cartel cuenta un mensaje importante. - At the demonstration, a young female politician explained to the citizens that each sign tells an important message.

la política (singular, usually with article) often = politics as a field:
- La política me interesa. = Politics interests me.
un político / una política = a politician (male / female):
- un político famoso = a famous (male) politician
- una política joven = a young (female) politician

So here política is a common noun for a female person, not the abstract concept.

Why is it una política joven and not una joven política?

Both una política joven and una joven política are grammatically correct, but the neutral, most common choice is una política joven (noun + adjective).

Subtle nuances:

una política joven
- Standard order: noun then adjective.
- Simply describes her as young, with no special emphasis.
una joven política
- Adjective before the noun can sound slightly more expressive, literary, or emphatic.
- Often heard in journalistic style, highlighting youth as a notable trait.

For everyday speech and for learners, una política joven is the safest, most neutral option.

Why is it en la manifestación and not something like a la manifestación?

The preposition en usually corresponds to in / at and describes location or the setting where something happens.

en la manifestación = at / in the demonstration (during that event, in that context)

If you said:

ir a la manifestación = to go to the demonstration (movement towards)
estar en la manifestación = to be at the demonstration (location)

In the sentence, the action (explaining) takes place within the event, so Spanish uses en.

What does manifestación mean? Is it a false friend?

Yes, it can be a bit of a false friend.

In Spanish, la manifestación commonly means demonstration / protest (people gathering to express their opinion publicly):

Hubo una manifestación contra la nueva ley.
There was a protest against the new law.

English manifestation is usually more abstract (the manifestation of symptoms, feelings, etc.), so it’s not the natural translation in this context. Here you should think: protest, march, demonstration.

How does explicar work with objects? Why explicó a la ciudadanía que…?

The verb explicar usually follows the pattern:

explicar algo a alguien
(to explain something to someone)

In the sentence:

explicó = (she) explained
a la ciudadanía = to the citizens / to the public → indirect object
que cada cartel cuenta un mensaje importante = what she explained → direct object (a whole clause)

So structurally you have:

[explicó] [a la ciudadanía] [que…]
explained [to the citizens] [that…]

Using a before la ciudadanía marks it clearly as the indirect object.

What exactly does la ciudadanía mean, and why is it singular?

la ciudadanía is a collective noun. It refers to the citizens as a whole, the general public, or the citizenry, and it’s grammatically singular:

La ciudadanía está preocupada.
The citizenry is worried. / People are worried.

It’s similar to English the public or the population, which are also treated grammatically as singular even though they refer to many people.

If you wanted to emphasize individuals, you’d use los ciudadanos (the citizens).

Is que here a relative pronoun (like who / which)?

No. In this sentence, que is a conjunction meaning that, introducing a subordinate clause that functions as the direct object of explicó:

explicó … que cada cartel cuenta un mensaje importante
she explained … that each poster conveys an important message

So here que does not refer to any noun; it simply links the main clause and the subordinate clause, just like English that in “She explained that…”.

Why is it cada cartel cuenta in the present when explicó is in the past?

This is a very natural use of the present tense in Spanish (and also in English) to talk about:

stable facts,
general truths, or
the content of something (e.g., what a sign, book, film “says”).

Even though the explaining happened in the past (explicó), the messages on the posters are still true and valid in the present, so Spanish uses the present:

explicó que cada cartel cuenta un mensaje importante
she explained that each poster conveys an important message

You could theoretically use a past tense (contaba), but it would sound more like those messages were only relevant at that specific past time or the situation has changed. The present here feels more natural.

What does contar mean here? I thought it meant to count.

Contar has two main meanings:

to count:
- contar hasta diez = to count to ten
to tell / relate / convey:
- contar una historia = to tell a story

In this sentence, cada cartel cuenta un mensaje importante uses the “tell / convey” meaning:

Each poster conveys / communicates / tells an important message.

You can think of it as very close to to tell or to express in English.

Why is it cada cartel in the singular? Could it be cada carteles?

Cada in Spanish is always followed by a singular noun, even though its meaning is distributive (referring to all members of a group one by one):

cada cartel = each poster
cada persona = each person
cada día = each day

So cada carteles is ungrammatical. You must say:

cada cartel cuenta…
each poster conveys…

What does cartel mean here? Is it related to (drug) cartel?

In this context, cartel means poster / sign / placard (like the signs people hold in a protest).

un cartel de la manifestación = a protest sign / poster from the demonstration.

The word for a drug cartel in Spanish is usually cártel (with an accent), though in practice cartel/cártel vary in writing. Context makes the meaning clear:

un cártel de drogas = a drug cartel
un cartel con un mensaje feminista = a poster with a feminist message

In your sentence, at a protest, it clearly means poster / placard.

Why is it un mensaje importante and not un importante mensaje?

Spanish tends to place adjectives after the noun as the default:

un mensaje importante = a(n) important message (neutral, most common)
un importante mensaje = also correct, but can sound a bit more formal, journalistic, or emphatic.

Adjective before the noun often adds:

emphasis,
a more subjective tone, or
a more literary / stylistic feel.

So un mensaje importante is the normal, neutral phrasing.

Can I say explicó la ciudadanía que… without a?

No. That would be incorrect here.

With explicar, the pattern is:

explicar algo a alguien
explain something to someone

a la ciudadanía works as the indirect object, introduced by a.
If you drop the a, la ciudadanía would be interpreted as a direct object, which doesn’t match the verb’s normal structure here.

So you need explicó a la ciudadanía que…, not explicó la ciudadanía que….