What’s the difference between a halakha and a mitsva?

Shalom, Thank you for your question. The Hebrew terms halacha and mitzvah each have specific meanings, but are sometimes used interchangeably. Halacha - this refers to the system of Jewish law in its widest sense. So the halacha talks about all areas of life and death, community, country, etc. To say something is "halacha" means that this way of doing things is not just a free choice, but rather proscribed as such through Jewish law. For example - "Rabbi, how nice of you to throw the trash in the bin after the picnic!" he said. To which the Rabbi responded, "Ah, but it's not just 'nice', it's a halacha!" This is to say that it's part of the Jewish legal system not to litter. Mitzvah - this comes from the word for "command", and means things that are commanded. There are mitzvot (plural of mitzvah) that were commanded by G-d, and those that were commanded by the Rabbis. Our tradition holds that there are 613 Torah Mitzvot, as well as more rabbinic ones. These are specific acts, such as putting on tefillin, giving charity, and celebrating Shabbat. As you can see, all mitzvot will also be halacha. But not all halacha is a mitzvah. For example, there is a halacha not to talk damaging gossip (lashon hara) - but it is not a mitzvah, as only positive commands can be a mitzvah. Also there are halachot about zoning laws, and building regulations, but these are not mitzvot. They are not specific acts that obligate a person, but rather general rules that apply in a certain situation. Beyond all this, there is a colloquial use of the word "mitzvah" which is used to denote that it is not halacha, but rather a nice thing to do! For example, "Go on, eat another piece of your grandmother's cake - it's a mitzvah!" As far as I know, it's a nice thing to eat your grandmother's cake, and it might even make her happy, but it is not a halacha stipulated by the Torah or the rabbis. May you merit to perform many mitzvot and live a life according to halacha! Blessings.