Does instance.new("Part", game.Workspace) create a new brick in the game when I run the script?

Technically, no. There is an error in it.

Instance.new("Part", game.Workspace)

would create a new brick when ran.

Read more about instances here

Instance.new("Part", game.Workspace)

The above script would Instace(Create) a "new" Part into game.Workspace.

You can also assign variables to set properties.

NewPart = Instance.new("Part")
NewPart.Parent = Workspace
NewPart.Size = Vector3.new(10,10,10)
NewPart.BrickColor = BrickColor.new("BlacK")
NewPart.CFrame = game.Workspace.UsernameHere.Torso.CFrame

You can also do many more.

Short answer: Yes

(the i in Instance needs caps)