What is option base? diff between option base and option explicit?

Option Base -

When an array is declared by default starting index number is 0. By using this statement the programmer can change the starting index number. Well but according to coding conventions this concept should not be used.

Option Explicit -

Declaring a variable in Visual Basic by default is not must. Due to this by default every variable are considered as Variant hence unnecessary memory wastage. Well good practice is to declare variable of the type you want to use. In case if you are not ware of the type u want to declare its better u declare explicit as variant. Well for this statement Option Explicit is used. this is set in top of General Declaration of Form Module. Once declared every variable type must be defined.