What is the real Catalan flag?
The Senyera is the Catalan official flag
The Senyera (which means “flagpole”, “standard”, “banner”, “ensign”, or, more generally, “flag” in Catalan) is a vexillological symbol based on the emblem of the Crown of Aragon, which consists of four red stripes on a yellow field. This emblem, often called the Aragon bar, or simply “the four bars”, historically represented the King of the Crown of Aragon.
The model of senyera is today in the flag of four autonomous Spanish communities (Catalonia, Aragón, Balearic Islands, Valencia), and is the flag of the Catalan-speaking city of Alghero (Catalan: L’Alguer) in Sardinia. It is also used on the emblem of Spain, the emblem of the Eastern Pyrenees and Provence-Alpes-Côte d’Azur, the flag of Roussillon, Capcir, Vallespir and Provence in France, a quarter of the coat of arms of Andorra and on the local flags of many municipalities belonging to these territories. The Senyera (sometimes together with the Andorra flag) is also used in a more informal way to represent the Catalan language.
The Estelada is the Catalan independentist flag
The Estelada is an unofficial flag typically flown by Catalan independentist supporters to express their support for an independent Catalan or independent Catalan of Països (Catalan lands, ie the territories traditionally speaking Catalan). The use of this flag as a symbol of protest within Catalan nationalism has become more notable since the Spanish transition to democracy in the 1970s. The design of the Eastelada includes the red and yellow bars of the Senyera, with the addition of a five-pointed star in a triangle to the hoist. It has not been adopted as the national flag of the proclaimed Catalan Republic, whose legitimacy is disputed; the flag of Senyera is used instead.