You buy one share of an aircraft - jet or helicopter - let's assume a 1/6th share.

Your cost of acquiring that share of the aircraft would generally be 1/6th of the cost of the entire aircraft, including the induction costs.

Depending on the percentage of your share and the aircraft you buy, you would be entitled to a certain number of hours of flying each year. For example, a 1/6th share could entitle you to 120 hours annually on a Cessna Citation II Jet.

You would of course own financial and legal interest in your aircraft to the extent of your share. The aircraft will be exclusively used by you and other owners, unless you have signed up for the fleet exchange program which entitles you to use aircraft owned by other owners and vice versa.

Once you become an owner, you would pay your share of the monthly management fee to cover the fixed expenses, including but not limited to pilots, crew, maintenance, airport services, insurance, hangar charges, administration etc. which are equivalent to your fractional share.
You then pay an hourly charge for whenever you utilize the aircraft. This covers fuel, airport charges and maintenance reserves.

As a Fractional Owner you have absolutely no management responsibility. The pilots, crew, ground staff, maintenance, administration and everything else is the responsibility of the Fractional Ownership Company. All you have to do is call your designated flight coordinator and show up at the airport.

If you plan to leave the program after a certain lock-in period, a good Fractional Ownership Program should guarantee to buy-back your share of ownership at a predetermined price.