Is there a difference between a program and a portfolio in project management companies?

Yes100 %, Programm related to specific line, it could be Business OR not , but its matching each other ,while Portfolio its financial term usually, related to business with diversifications- most probably.

Yes, The components of a program are related to each other while in case of portfolio the components may not necessarily be interdependent or directly related. 

I agree with Mr. Sahl HIJAZI in his answer.

Agree with Mr. SAHL HIJAZI

Yes. Prgrams are composed on multiple projects whicl portfolios have abusiness scope related to the strategic goals of the orgnization. Protfolio managers monitor aggrigate performance and value indicators while program managers monitor prgress of program components. Portfolio success is measured in aggregate performance of portfolio components while program success is measured to the degree of its components.