Make a hole at the bottom of the plastic bottle. Pinch the hole with your finger and pour into a bottle

Make a hole at the bottom of the plastic bottle. Pinch the hole with your finger and pour into a bottle of water, close the neck with a lid. Release your finger gently. The bottle will not pour out of water. Now open the cover carefully. Water will pour from the hole. Explain the observed phenomenon.

Water from a bottle with a twisted cork will not pour out, because only the internal pressure in the bottle acts on it, and it is not enough to squeeze out the water. But as soon as we open the lid, the water will begin to pour out, since atmospheric pressure will still begin to act on the water, and it is already capable of pushing the water out of the hole.