Nails are small pieces of metal with one sharp end and one end that is flat. You use nails to stick things to other things, like nailing a piece of wood to another piece of wood. You use a hammer to hit the flat end of the nails with to push them through something.
A gap between two things is narrow if the two things are quite close together and there is not a lot of room between them. The street in the picture is very narrow. The opposite of narrow is wide.
Nasturtiums are a common plant grown for their pretty flowers. Nasturtium's leaves and flowers are edible and can be used in salads. Nasturtiums attract good insects to the garden and repel bad ones like some caterpillars and are often grown as companion plants around a vegetable garden.
Some people call a kind of watercress a nasturtium.
Your neck is between your head and your body. Your neck is sometimes called your throat. It has several bones in it, and can turn in a variety of directions. People like to wear jewellery around their necks.
A necklace is a pretty piece of jewellery that is worn around the neck. Necklaces are usually made of chain, or a string threaded with beads. Sometimes a pretty pendant is hung from the necklace.