Learn Hardcore Spanish (Spain): Ese foro en el que escribimos es mi red social favorita. - That forum in which we write is my favorite social network.

este foro – this forum (close to the speaker, or just mentioned, very “present” in the conversation)
ese foro – that forum (not so close to the speaker; often the “normal” choice for something neither very near nor very far)
aquel foro – that forum over there (far from both speaker and listener, or “far” in time / emotionally / in the discourse)

In everyday modern usage, ese is often the default for “that” when you’re just talking about some forum that isn’t right “here,” especially online.

You could say:

Este foro en el que escribimos… – if you feel very “close” to it, e.g. “this forum we’re using right now.”
Aquel foro en el que escribimos… – if you want to stress that it feels distant (maybe a forum you used a long time ago).

But with no special nuance intended, ese is the most natural choice for plain “that forum.”

Why is there en el que instead of just que?

In Spanish, when a relative clause depends on a preposition, that preposition must stay in front of the relative pronoun:

We write in that forum → escribimos en ese foro
That forum in which we write → ese foro en el que escribimos

You can’t say:

✗ Ese foro que escribimos (missing the preposition en)
✗ Ese foro en que escribimos (understood in some regions, but en el que is safer and more standard/formal here)

So the preposition en (“in / on”) has to appear before the relative pronoun, and Spanish typically uses el que (or el cual) in these cases:

El foro en el que escribimos = The forum in which we write
La página en la que entro cada día = The page I go on every day

Could I say Ese foro donde escribimos instead of Ese foro en el que escribimos?

Yes, you can. Both are correct, with slightly different style:

Ese foro en el que escribimos – a bit more explicit and somewhat more formal / careful.
Ese foro donde escribimos – a bit shorter and more colloquial-sounding.

In practice, both are very common and usually interchangeable:

Ese foro donde escribimos es mi red social favorita.
Ese foro en el que escribimos es mi red social favorita.

There is no important meaning difference here; it’s mostly stylistic.

Why is it en el que and not en lo que?

The article in el que must agree in gender and number with the noun it refers to.

foro is masculine singular → el foro
So we need en el que (masculine singular) to refer back to foro.

Examples:

El foro en el que escribimos (masc. sing.)
La página en la que escribimos (fem. sing.)
Los foros en los que escribimos (masc. pl.)
Las páginas en las que escribimos (fem. pl.)

Lo que is different: it’s neutral and means “what / the thing that,” not “which” referring to a specific masculine noun.

Lo que escribimos = What we write / The thing that we write (not referring back to foro)

Why is escribimos used without the subject nosotros?

In Spanish, subject pronouns (yo, tú, él, nosotros…) are usually dropped because the verb ending already shows who the subject is:

escribo = I write
escribes = you write
escribe = he/she/it writes
escribimos = we write
escribís / escriben = you (plural) / they write

So en el que escribimos already means in which we write. Adding nosotros is possible but not necessary:

En el que nosotros escribimos – correct, but usually only used for emphasis or contrast (e.g. we write there, not them).

Does escribimos here mean “we write” in general, or “we are writing right now”?

In Spanish, the simple present (escribimos) can express:

A general / habitual action:
- En ese foro escribimos todos los días.
  = We write on that forum every day.
A present-time ongoing action, especially in some contexts:
- ¿Qué hacemos? Escribimos en el foro.
  = What are we doing? We’re writing on the forum.

In your sentence:

Ese foro en el que escribimos es mi red social favorita.

It’s most naturally understood as a general/habitual action: that forum where we (usually) write / where we post.

Why is it mi red social favorita and not mi favorita red social?

Spanish normally places adjectives after the noun:

red social favorita = favorite social network
(literally “network social favorite”)

Putting favorita before red social would sound wrong here. Many adjectives occasionally go before a noun with a special nuance (e.g. gran idea), but favorito/favorita normally goes after:

mi libro favorito, mi canción favorita, mi lugar favorito

So the natural order is:

mi red social favorita
not
✗ mi favorita red social

Why is favorita feminine? What is it agreeing with?

Favorita is feminine singular because it agrees with red, which is feminine singular:

la red → feminine singular noun
social → adjective describing red, also feminine singular (same form for masc/fem here)
favorita → adjective describing red, must match its gender/number

So:

mi red social favorita
- mi – does not change for gender/number
- red – feminine singular noun
- social – invariable in gender (same form)
- favorita – feminine singular to agree with red

If the noun were masculine, favorito would change:

mi foro favorito (masc.)
mi blog favorito (masc.)

What exactly does red social mean? Is it the same as “social media”?

Red social literally means “social network.”

red = network
social = social

In practice, red social is used very much like English “social network”, and often overlaps with the everyday use of “social media”:

Facebook es una red social.
Instagram y TikTok son redes sociales.

So mi red social favorita is naturally translated as:

“my favorite social network”
or, more loosely,
“my favorite social media platform.”

Could we say es mi red social preferida instead of favorita?

Yes. Preferida and favorita are very close in meaning:

mi red social favorita
mi red social preferida

Both can mean “my favorite social network.”
There can be subtle style or regional preferences, but for most learners they are interchangeable here.

Can I change the word order and say Mi red social favorita es ese foro en el que escribimos?

Yes, absolutely. Both are correct:

Ese foro en el que escribimos es mi red social favorita.
Mi red social favorita es ese foro en el que escribimos.

Spanish, like English, allows both:

That forum … is my favorite social network.
My favorite social network is that forum …

The choice is mostly about emphasis:

Starting with Ese foro… puts more focus on that specific forum.
Starting with Mi red social favorita… highlights the idea of your favorite social network first.