What is a portfolio?    

A portfolio is a collection of products or results to illustrate a persons capabilities. For example  artists and architects present a portfolio with work, photographs of products and recommendations of clients to convince the new client or customer, that he or she is the right person to get a job or assignment.

Many companies use portfolios to show the kind of projects or business they are good in to obtain new orders.

In education the portfolio is a collection products and evidences to give an impression of what the student has learnt and is able to do.

A definition: “The term portfolio as used in the UK generally describes a collection (or archive) of reflective writing and associated evidence, which documents learning and which a learner may draw upon to present her/his learning and achievements. A portfolio therefore encompasses the concept of personal development records (PDRs) ...() ."