A bank is a place you go to deposit or withdraw money, or ask for a loan to buy a house or car. Bank buildings are not as common as they used to be, as you can now do a lot of banking via an ATM or over the Internet.
Something is blank if there is nothing on it yet. Things that are usually described as blank when they are new are pieces of paper, an artist's canvas, or a computer storage device like a hard disk. These are all things that are blank before you write on them.
A fish tank is a glass container you keep pet fish in. You can also keep turtles, hermit crabs or even mice, lizards, frogs and snakes in a fishtank. Obviously, if you are keeping land animals in a fish tank you don't fill it with water, you put dirt in the bottom and grow plants. A fishtank with plants in it is often called a vivarium. You usually keep mice in a fishtank with sawdust at the bottom instead of dirt, so you can regularly change the sawdust to keep it clean.
Frank is a French name for boys. Frank means "free." The man in the picture is singer Frank Sinatra.
A piggy bank or money box is a container you use to store coins, and are usually used by children to save money. Piggy banks can be any shape but are most commonly shaped like a pig. They have a slot in the top to put coins in, and an opening at the bottom to get them out again.
Planks are wide pieces of lumber. Planks are generally quite large - a smaller, thinner plank would be called a board.