What is the difference between leasing and chartering?
Leasing is just a long term rental of the chattel, the airplane itself, where the lessee entity does whatever it wants with the airplane during the period of lease. So you lease an airplane from a leasing company like GE Capital, and do whatever you want with it until the lease is up, then return it.
A charter is a more restrictive and objective-focused contract: it's an agreement to use aircraft for a specific purpose defined in the charter contract.
So if I want an airplane for a year to be at my beck and call to do whatever I wish, I lease it for a year.
If I want an airplane for a specific purpose, like transporting my football team around between cities X, Y  and Z for a month, with no other uses allowed unless specified in the contract, I charter it.
Usually, the charter contract is &quot;turn key&quot; and will include crew and support services, whereas with a lease, the user is only getting the airplane and has to provide all that themselves.
You can also have all-inclusive leases, called &quot;wet leases&quot; that include crews and maintenance, possibly even fuel, built into the lease rate, but you still have freedom to use the plane however you wish, as opposed to a charter where the use of the aircraft is specified in the charter.
An airline might wet lease an airplane when they need a short term replacements for grounded aircraft, especially if the type is different from their fleet.