I thought that "a cat" meant "one" kind of animals, but not "one" cat. Now that I think "a cat" means "one cat" and "cats" means all cats that are one kind of animals. Is it true?　I'm confused.

Some examples to help you. I like cats (all) because they are very soft and gentle. I like cats (all) because they are friendly and want to be petted. I like the cat that has the green eyes. (one specific cat) I like the cat that is sitting in the window of my apartment. (one specific cat that you know) I like the cat whose name is Hana.(one specific cat that you know) I like the cat that is black and white. (one specific cat that you know) I like a cat that lets me pet it. I like a cat who is friendly I like a cat that is quiet

TO Pham Thank you for such a usefull online page.I'll read it carefully. TO Rene Thank you! I'll read your comment again and again. TO Tony Thank you! I'll read your comment again and again. All comments really help me.

Yes, you are right by the meaning of "the cat" which means a specific cat you like. It must be the cat you have mentioned before or both you and the listeners know. A cat basically can mean any cat but just one in number. I like cats just mean cats in general, can be any cat, like "猫が好き". Hope it helps.

"I like a cat" means either there is only one cat you like or you like some cats but just now you start to talk about ONE cat that you like and you have not mentioned this cat before. So, you are talking about one specific cat. "I like the cat" is actually similar to the previous. But this can be used only if you or another person has already mentioned the cat. For example: "My neighbour has a cat. I like the cat." "I like cats" means that you like (all) cats. Maybe not all, maybe there are some crazy cats you do not like, but IN GENERAL you like cats. All those sentences are correct if used in correct places.