What can you use to get rid of weeds and plants permanently?

Use "Roundup". It will kill all vegetation. Do not plant anything for at least three months afterward.

what kind of plants?

You can use newspaper or heavy landscape cloth to smother them. Not helpful if there are other plants you want to save-I hand weed and use a heavy mulch (not compost-use a cedar mulch ) to help beat the weeds down. I generally do not use Roundup or Preen as I have pets and live over a stream and don't want to poison anything. (I will use Roundup on poison ivy though-I spray it on the leaves and let it slowly kill the plant.)

Roundup is horrible and is partially at fault for killing off our bee hives. Please don't use it. Nothing is permanent...weeds will always find a way. You can try smothering them with newspaper, kept wet or make a 50/50 mixture of vinegar and water with an added tsp of Dawn dish soap. Don't spray this on a windy day or on anything you don't want to kill. It works pretty fast.

Hot salt water will kill any plant.....or cold salt water.....spray or pour on plants

Get rid of weeds permanently? Never ever gonna happen. They fly through the air will nilly in the slightest breeze, all you can do is plant properly with weed barriers and pluck the ones that come up. Till you soil in the garden bed, amend as needed. Lay down landscape cloth, cardboard or newspaper. Plant your plants in ground taking care to make sure they have room to "breathe" and then top with mulch of your choice. Now the weeds that do apoear are on top and shallow rooted and easy to handle. Happy gardening! 🌱

I'll try it. Weed killer gets expensive.