صديق  friend, any friend.

زميل colleage in a study or work.

حليف means ally, the one who supports you according to a treaty.

خليل very close friend who is devoted to you.

صاحب a companion who is asociated with you.

جليس  sitter"always sits with you like the one who sits with kids at home or with an ill person at hospital.

جليس means literally

But we say it to mean that someone who is being always with