hello! "ca" is more common (familiar language) in conversations but "cela" is the same thing but says more with a courteous language. It is used to indicated something (in english this or that) Je ne sais pas si mon anglais est bien ^^ désoler

Indeed, ça is a contraction of cela. Remember to use the ç because "ca" could exist but it's a mistake, You can just find Ca or ca when you can't have the ç on your keyboard...