Catalan is a romance language and originated from Latin (as did Spanish, French, Italian and others). It has also been influenced along the way by basque, arabic and the germanic languages.
And of course Spanish.
Catalan is spoken throughout Catalonia and the Balearic islands by around eleven million native speakers. It was repressed (as were other minority languages in Spain) through the Francoist dictatorship, but has since been recognized as one of Spains official languages. The wiki as usual has a thorough entry on this topic.
Although Catalan is considered a minority language, it is worth remembering that it spoken over an area of more than 60,000 square kilometers, an area bigger than some nation states.
According to Ethnologue , the lexical similarity (a measure of the degree to which the word sets of two given languages are similar) between Catalan and (some) other Romance languages is : 87% with Italian, 85% with Portuguese and Spanish and 73% with Romanian.
Even assuming this data to be on the high side (e.g. according to a Ethnologue the lexical similarity between English and German is 60%), it demonstrates not only that Catalan is closely linked to other romance languages, but that knowing another romance language is a massive advantage in learning Catalan.
This question is frequently asked about languages, and the answer as always is 'it depends'.
If you are a native speaker of (for example) Spanish, Italian or French, you will find it quicker and easier to learn Catalan than (for example) a native Russian speaker, due to the similarities between the languages.
If you are an English speaker who speaks Spanish or another romance language well, again you will be able to learn Catalan faster than a monolingual English Speaker.
And so on.
Catalan grammar is similar to other romance languages. (Of course this is only helpful to know if you happen to speak another or the romance languages).
Articles Catalan has both definite and indefinite articles which decline according to gender and number and agree with the corresponding noun.
Nouns Catalan nouns are inflected for gender (masculine or feminine), and number (singular or plural). There is no case inflection. Articles and adjectives agree in gender and number with the noun they refer to.
Catalan grammar has more information on the structure of the Catalan language along with examples, phrases and so on.
The wiki page contains much more (somewhat dense) information about Catalan grammar.