It's known as "neem" in English, and "nim" in Spanish. It originated in India, where it is known as the "pharmacy tree", was planted by the thousands here in the DR, but either was underpromoted for its uses, or the dominicanos didn't listen to the explanations, hehehe.
Indians have used this tree for 5,000 years, but no one here in the DR seems to want to know anything about it, they just know that it heaves sidewalks, and that nothing will grow in its deep shade. In other countries, farmers use it for the shade for their cattle, which can also rest unmolested by insects under its branches.
The tree and its qualities do not immediately kill insects, but rather interrupt insects reproduction, and in time, eliminate most of them in the area.
Its leaves and twigs will help eliminate most oral/dental problems as an antiseptic agent in the mouth. One can either use a twig as a toothbrush/flossing tool, or one can chew (but not swallow) a few leaves every morning, spitting out the residue after a few minutes of chewing, and then not rinsing your mouth until at least 15 or 20 minutes later.
The drawback is that it tastes very bitter, and a bit garlicy, but the good outweighs the bad for me.
The seeds must be planted relatively soon after falling from the tree, as they are only viable for about 15 or 20 days. They sprout easily, and grow quickly. Neem will take anything, bad soil, dry soil, wet soil, but they do not tolerate salty conditions very well, so you can't do well with neem near the ocean. If you give a young tree a bucket of water once or twice a week, it will grow to 20' in the first year. You can top the trees, and use the branches for fenceposts, which also resist rot better than most wood.