Video by coreyyy.exe on Instagram.
The Catalan language is located in the middle of the Western Romance language continuum.
Romance languages (languages that derive from Latin), each with its own regional varieties, form a continuum: every town can understand the towns next to them, and the next town will understand the towns next to them; but, the farther away you go, the more it will have changed. Since Catalan is located at the centre, it's the most easily understandable one, and Catalan speakers have it the easiest to understand all others.
However, there is another variable that should be taken into account when we discuss how understandable languages are: this other variable is familiarity. All Romance language speakers are familiar with Spanish, Italian, and French. Even if they don't speak them, they have heard them, are familiar with their sounds, know some words and sentences, etc. The same is not true of Catalan, as a result of the historical discrimination against Catalan in recent history. As a result, people might be confused at first when hearing Catalan sounds, but after a couple of minutes of listening they will start to understand it.
Catalan language has two main accents (with smaller variations inside each of them): Western and Eastern. One of them is the perfect accent to be easily understood, too.
Western Catalan is spoken in the Western half of Catalonia (Barcelona, Perpinyà, Girona, etc) and the Balearic Islands, while Western is spoken in the Western half of Catalonia (Lleida, Tortosa, etc), Andorra, the Valencian Country, and the Aragon Strip.
The main difference between Eastern and Western Catalan accents is that the West has a very clear pronunciation, where each sound and especially each vowel is very clear and unambiguous, having the same sounds as Italian. Italian is often considered the most easily understandable Romance language (out of the famous Romance languages) precisely because of its clarity in pronunciation.
On the other hand, Eastern Catalan's vowels are less clear, because the unstressed As and Es are pronounced like a ə (a middle point between A and E) —reaching the extreme in many accents of the Balearic Islands, where all As and Es are pronounced as ə. This makes Eastern Catalan pronunciation more similar to French, when it comes to vowels. This fact can make listening a bit harder for the first times a speaker of another Romance language encounters Eastern Catalan, but as soon as you've picked up on it then you're good.
Summing up: Catalan spoken in its Western accent would be the "bridge" language between the other Romance languages.
Do you want to give it a try? If you speak another Romance language, how much can you understand? Here's an example: the girl who makes the video (Roser Regolf) and the first person she talks with speak Catalan with a Western accent, while the other people she talks with speak Catalan with an Eastern accent.
Say in the tags how much you could understand!