A ‘mala’ is a case made out of plastic, leather, canvas, vinyl or some other sturdy material, with a hinged lid and a handle to make it suitable for carrying clothes and other luggage. So a suitcase or trunk.

Here's a typical one: http://entretenimento.r7.com/blogs/giuseppe-oristanio/files/2014/02/como-fazer-mala-1.jpg

It can also be a woman's handbag, more or less synonymous with ‘bolsa’, or the boot of a car, or slang for someone's stomach or abdomen.

In Brazil it can informally also mean a bore (in the sense of a boring person) or it can be a vulgar word for anus or penis.

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A ‘maleta’ is a small suitcase, typically one of those on little wheels with an elongated handle that you drag along behind you.

Here's an example: http://milvuelosbaratos.com/wp-content/maleta.jpg

But it can also be used for a variety of other kinds of small suitcases.