Alicorns contain the natural connection to Equus of earthponies, the ability to fly and affect weather as pegasi do, and the power to manipulate Equus' magic sphere as easily as the unicorns. They can either be created through an intense magical process fulfilled by another alicorn [or powerful being], or by being born naturally as one [when one parent is an alicorn already]. The alicorn was created as the hopeful solution to the war that broke out with the introduction of unicorns to Equus. The Guide known as Life worked alongside Peace to form an entity that would combine the strengths of all of the current pony races. At first, their attempts were received negatively, and those prototypes eventually became the Angels that watched over the ethereal realm. But eventually, the alicorns Solaine Celestia and Selena Luna were born, their arrival bringing an era of peace. The alicornification process is a long-revered process that only the alicorns themselves oversee, like Twilight's mentorship under Celestia.
The first of Life's attempts at creating complex, sapient life. As the guides were all relatively young, they had many flaws in their creation process, and many 'fixes' that would affect the formation of other races of pony. Earthponies are very worldly, sturdy creatures with an innate connection to nature and Equus itself. Often, their talents are based in environmental and agricultural prowess. At first, ponies did not have pre-destined talents, but after watching Her creations fumble around for a while, Life bestowed the Cutiemark unto the earthponies. The unique process was also given a physical stamp of identification on their flank, making it easier for communities to delegate work. After a while of being left to their own devices, earthpony societies began practicing alchemy to better understand the magical element of their world. The quality of life and efficiency of their farms were dependent on the fluctuating weather patterns, and their complaints of drought and flood reached Life, who began work on the next addition to Her creation project -- the pegasus.
After the earthponies started poking around Equus for knowledge on how to potentially affect the weather, Life worked with Feast to create the pegasi. A unique form of pony, with feathered wings and lighter bodies to allow for flight, they were seen as miracles and sometimes depicted as the guides' first angels. Their talents leant towards the elements, moving around clouds and sun rays, and generally being a huge aid to the earthponies' agricultural efforts. In return, the earthponies shared their food with the pegasi, and the two races intermingled freely. The addition of the pegasus race to Life's project made Her hopeful that new creations would be as easily accepted. Once the two species dipped their hooves further into alchemy and magical study, She knew what to create next -- a race whose body would be a conduit and container of magical energy, that would allow pony society to flourish in new and exciting ways -- the unicorn.
The third addition to the creation project Life started. Unicorns were a little trickier than the other races, as while She had struggled at first with each iteration, the ancient unicorns were not able to properly store their magical energy, and health complications arose. However, it wasn't until a few generations of these unicorns had been allowed to interact with other ponies that the guide, Health, noticed, and brought it to Life's attention. Together, they worked to fix these abnormalities, and the second attempt proved fruitful. Unicorns' bodies conduct and absorb magical energies much easier than earthponies or pegasi, and their horns are where it is released. Their natural connection to the magical and ethereal fields make them very powerful, and potentially very dangerous. As a result, early unicorns were often shunned and feared by the other two races. This tension eventually led to a war, one that raged on for centuries before Life and Peace embarked on their newest project, some creature that could unite the species and bring peace back to Equus. This goal eventually led to the alicorn sisters' conception.
Despite the growing population within pony society, batponies were not created by Life or any of the other known guides. In fact, the origin of the nocturnal race seems to be the Everfree Forest, where the unknown entity that calls it home formed its first creations. Batponies are very similar to pegasi, with a few key differences -- their appetite for meats, their night vision, and the most prominent, their fleshy bat wings. As well, they have no connection to weather, seeming to have more night and magic based talents, if any at all. It's unsure why they were created, just that it happened a few thousand years after the alicorns were introduced, and with seemingly no intentions of mixing the populations. Most batponies hail from the Everfree itself, or from the isolated batpony kingdom of Hollow Shades. While their conception was later than the other races, by the time they'd been discovered, the alicorn sisters had been ruling and enacting unity measures for millenia. That doesn't mean they're free from discrimination, though, as many ponies find their carnivorous habits revolting.
Life is not the only guide capable of creation, though She is often the arbitor of it. If another guide, or entity, wants to, they can attempt the process, though it is grueling and draining. Draconequus like Discord or Dulcet, the Everfree Entity, and even some magically-heightened ponies have been able to sustain new life. The main categories of non-Lifemade species are the breezies formed by Dulcet, changelings invented by War, chimeras created by the Everfree Entity, and starslugs made by Quench. Many more exist, some just curious experiments by Life or other guides, others formed in their own way through evolution and environmental change. They are often unable to gain Cutiemarks like normal ponies, but may have magical prowess or abilities that rival the other species.