One of the biggest mysteries of physics (and life, the universe, and everything) is this: why is anything even here?
antimatter were, per theory, created in equal quantities. So: why didn't the universe's matter and antimatter eradicate each other and leave behind nothing but energy?
(I'm not complaining that we're here. Merely puzzled.)
I have no answer for either question, but I admit to an interest in all things antimatter. When matter and antimatter (of matched particles, like proton/antiproton or electron/positron) meet, the result is horrific explosions. Mass and energy stand in a fixed relationship, per what is perhaps the best-known equation in physics -- E = mc squared (sorry I can't enter a superscript on blogspot) -- so we know exactly what radiation results: gamma rays with very specific energies. (It's a bit more complicated for proton/antiproton annihilation -- some secondary particles are produced along with the gamma rays. For electron/positron encounters, though, the byproduct each time is simply a photon carrying 511 KeV of energy.)
SF writers like antimatter because matter/antimatter annihilation is the most compact way to store energy -- whether for superweapons or to fuel interstellar travel. The challenge is in having any antimatter to store. Antimatter has to be created one antiparticle at a time. E = mc squared being a symmetric relationship, we have to provide a lot of energy to create a little antimatter. Then we have to store that antiparticle without it touching anything ... or boom.
Antimatter is produced, antiparticle by antiparticle, in extremely high energy collisions of regular-matter particles inside huge particle accelerators. Using magnetic fields, the (for example) positrons are captured from the subatomic debris. The antimatter is then held isolated by magnetic traps -- if the antimatter touches the wall of a physical container: bye-bye, antimatter.
As you might expect, antimatter produced this way doesn't come cheap. In a 1999 article, NASA said they could produce antimatter for $1.75 quadrillion an ounce. (Passing note: industrial-scale antimatter production plays a big part in my novel InterstellarNet: New Order.)
Antimatter caught streaming from thunderstorms on Earth. Positrons, to be specific: the tell-tale gamma rays of their subsequent destruction have been caught in satellite observations.
Alas, capturing antimatter in the middle of an upper-atmosphere lightning storm doesn't seem practical.