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Equipment
"Professional-grade" equipment is built to higher standards than "consumer grade" equipment. Copyright laws that require copy protection in consumer equipment sometimes contain exemptions for professional grade audio (audio tape, CD) and video (VHS, DVD players) equipment ( see Digital Millennium Copyright Act http://en.wikipedia.org/wiki/Digital_Millennium_Copyright_Act ).
This equipment is usually more expensive and sometimes unavailable to the general public. The term may however also be used as a simple marketing ploy, as it is normally not protected or legally defined.
http://en.wikipedia.org/wiki/Professional

About Work

Definition
A professional is a worker required to possess a large body of knowledge derived from extensive academic study (usually tertiary), with the training almost always formalized.

Professionals are at least to a degree self-regulating, in that they control the training and evaluation processes that admit new persons to the field, and in judging whether the work done by their members is up to standard. This differs from other kinds of work where regulation (if considered necessary) is imposed by the state, or where official quality standards are often lacking. Professions have some historical links to guilds in these regards.

Professionals usually have autonomy in the workplace—they are expected to utilize their independent judgement and professional ethics in carrying out their responsibilities.[4] This holds true even if they are employees instead of working on their own. Typically a professional provides a service (in exchange for payment or salary), in accordance with established protocols for licensing, ethics, procedures, standards of service and training / certification.

The above definitions were echoed by economist and sociologist Max Weber, who noted that professions are defined by the power to exclude and control admission to the profession, as well as by the development of a particular vocabulary specific to the occupation, and at least somewhat incomprehensible to outsiders.[citation needed]

Therefore it would be appropriate to state that a 'true' professional must be proficient in all criteria for the field of work they are practising professionally in. Criteria include following:

1. The highest academic qualifications - i.e., university college/institute
2. Expert and specialised knowledge in field which one is practising Professionally
3. Excellent manual/practical & literary skills in relation to profession
4. High quality work in (examples): creations, products, services, presentations, consultancy,
primary/other research, administrative, marketing or other work endeavours
5. A high standard of professional ethics, behaviour and work activities while carrying out one's
profession (as an employee, self-employed person, enterprise, business, company, or partnership/associate/colleague, etc.)

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Well,
I'm happy that I'm a pro amateur having a lot of fun playing (read: pressing buttons and keys)
on a modern "toy" called arranger keyboard, karaokemachine, midifileplayer or whatever!
Sometimes it even happens that somebody manage to guess what tune or song I'm trying to perform.

Happy Playing
GJ