The photonic torpedo is equipped with a variable yield antimatter warhead. It has over fifty times greater range than the spatial torpedo. The variable yield was described by Malcolm Reed as being able to "knock the com array off a shuttlepod without scratching the hull, or put a three-kilometer crater into an asteroid." Antimatter to the warheads on NX-class starships is provided by the ship's antimatter reserves. (ENT: "The Expanse", "Hatchery")
Starfleet began to utilize the technology in 2153, when it began installation of the torpedoes aboard the Enterprise NX-01 following its return to Earth. These new weapons were installed in the ship's armory to better prepare them for the search for the Xindi superweapon. (ENT: "The Expanse")
The use of antimatter warheads aboard Earth starships came as quite a surprise to attacking Klingons. In 2153, they sustained enough damage that they were forced to discontinue their pursuit of Enterprise on course to the Delphic Expanse. However, this form of torpedo still could not effectively penetrate the deflector shielding of a typical Klingon Bird-of-Prey when most shield power was transferred to the section under attack. (ENT: "The Expanse")
Klingon torpedo technology of the time, nevertheless, appeared to be much more advanced than both Earth and Vulcan technology, as some of their ships were already equipped with photon torpedoes. (ENT: "Sleeping Dogs")
In the mirror universe, photonic torpedoes were already in use on the Emmette-type starships. The weapons were used during an assault on the Lunar colonies, that occurred some time before the introduction of the NX-class of starships in 2151. (ENT: "In a Mirror, Darkly", "In a Mirror, Darkly, Part II")
It became something of a Starfleet tradition to place dead crewmembers inside an empty torpedo casing, and often such torpedoes were launched into space. For such a burial in space by the crew, the Captain of the starship often conducted the funeral service.
The precise distinction between photon and photonic torpedoes remains unclear, since both seem to have antimatter warheads with variable yields, and the casings for 22nd century photonic torpedoes and 23rd and 24th century photon torpedoes are very similar. It is possible that "photon torpedo" is a shortening of the original term, similar to the way "cellular telephone" has been shortened over time to simply "cell phone." This possibility is supported by VOY: "Living Witness", in which the 31st century Kyrians describe a Starfleet photon torpedo as a "photonic torpedo." However, in ENT: "Sleeping Dogs", when Hoshi Sato and Malcolm Reed examine the controls of a derelict Klingon Raptor-class ship, both are puzzled by a description (in Klingonese) of "photon torpedoes," although Reed and T'Pol are subsequently able to use the torpedoes with reasonable effectiveness.
If photonic torpedoes are different from the later photon torpedoes, it is unclear when Starfleet upgraded to the later weapons, although the change had apparently been made by 2233, as seen in Star Trek. The Star Trek: The Next Generation Technical Manual indicates that Starfleet began work on the photon torpedo in 2215. ENT: "Sleeping Dogs" indicates that the Klingon Empire had photon torpedoes as early as 2151.
According to StarTrek.com, photonic torpedoes were in fact the earliest model of a Starfleet photon torpedo. Photonic torpedoes were also armed with a matter/antimatter charge and an optional timer. They had simpler internal systems than the spatial torpedoes. For storage, the torpedoes were powered down to a safe mode to protect them from a failure of the magnetic field around the antimatter charge. 
A photonic torpedo casing was auctioned off in the It's A Wrap! sale and auction.