How program management, and portfolio management are different?

-Portfolio management is focused on the decision-making process around which programs and projects should be executed based on their alignment with the goals and objectives of the organization.

-Program Management focuses is on achieving cost, schedule, and performance objectives of the projects within the program i.e. intermediate layer that is focused on the delivery of business benefits.

-Project Management is largely concerned with achieving specific deliverables that support specific organizational objectives. 

Multiple projects in the same business area make up a program, and multiple programs in the same business area make up a portfolio. To manage the portfolio, one needs to know everything and manage effectively  the projects and programs that lie in the purview of the portfolio.

I can see the main thisng here is that program mangement concern more about long term & stratigic projects & how to reach & achieve it & portfolio is concerning more about existing projest to be executed as per company's goals.

portfolio management

includes two or more of programs management

Protfolio management is a mean to reach strategic goals of an organisation, so projects can be independent, and concern différent objectives. A Program is a set of projects that have a common  objective, a Portfolio can contain one or more programs

Portfolio management is at enterprise level, aligning organizational strategy, supports decision making whereas programme management is supporting the execution to achieve the goals 

Almost the same thing except that the latter could constitute multiple projects.