I HAVE BEEN LEARNING HILCHOT TZEDOKAH IN THE SHULCHAN ARUCH AND HAVE RARELY SEEN REFERENCES TO MAASER KESAFIM. YET THERE ARE MANY PEOPLE WHO CONFUSE THE TWO AND SAY THEY ARE TODAY ONE AND THE SAME THING. SURELY THIS CANNOT BE CORRECT. TZEDOKAY IS A TORAH MITZVAH FOR ALL TIMES WHEREAS MAASER KESAFIM SEEMS ONLY A MINHAG OR RABBINIC DECREE. WHY IS THERE CONFUSION?
Answer:
It is true that there is some confusion between the two. The actual Torah obligation to give charity, which applies even to poor people, comes to a very small yearly amount. The concept of ma'aser, however, does not apply to poor people, and most authorities understand it as a custom. The reason why the two are confused is because ma'aser quantifies charity--one gives 10 percent to charity--and therefore it is seen as the obligation of charity itself.
Please see https://dinonline.org/2010/08/12/laws-of-tzedakah-part-i-the-basic-obligation/ for the basic obligation of charity, and https://dinonline.org/2010/11/11/vayeitzei-the%C2%A0basics%C2%A0of%C2%A0maaser%C2%A0kesafim/ for the basic concept of giving maaser.