Logic is implementation of the business rule, dependency into software code which adheres to platform syntax and standards.
Logic is the source for solution - business
Logic is the key for achieving the requirement constraints or conditions.
Ex: Consider a Retail transaction
MRP of a product shall be the sum of Selling price and profit subtracting discount if any.
Logic would have to be something like this,
If (discount == true)
MRP (variable) = ( SP (variable) or source + Profit(variable) or source ) - Discount (variable) or source
MRP (variable) = SP (variable) or source + Profit(variable) or source
Thus computer can process the language it knows, mathematical implementation has to be converted into computer/software implementation using a Platform i.e. programming language.