"some people use it to store honey or jam."

Yes. A jar is a container like a small bottle; it is often made of glass; and it can hold jam or honey. Use "it," not "he." Use "he" for men, "she" for women, and "it" for things. To make the statement more complete, I would add details. "A jar is a container. It is like a small bottle, with a wide mouth. It is usually made of glass or plastic. It has a lid. It is well sealed. It can hold many things. It can hold wet things like jam or honey without leaking."