Learning more information in Visual Basic 2015

Hi!
I want to know what is the use of functions? What are the different syntaxes that I can use for the functions? Can you provide me description for each function? What is the use of input box? Can you show me the declaration using an input box? What do you mean by CSng? What is the use of it? What is the meaning also of LCase? What is the use of it in VB program? Why do we always have to use “Val” in declarations or syntaxes?
Please help me with this!
Thank you!
