There's a "High School to Flight School" program for Army warrant officers. You go straight to being a WO. Indeed, most Army WOs/CWOs you hear about are helicopter pilots but there are nearly 50 specialties open to them. Most of the non-flyers are high-performing enlisted personnel who wanted to specialize and have the additional leadership opportunities.
You're a WO-1 (Warrant Officer) for about 2 years, then a CWO-2 through CWO-5 (Chief Warrant Officer) thereafter. Promotion comes every 5-6 years for someone on track. All warrant officers are officers and since the 1990s, all CWOs are commissioned (though they're not what you think of when you use the term "commissioned officer"; remember, corporals and sergeants are (non-commissioned) officers too, as they can give orders which, if lawful, must be obeyed). A big difference: Officers are generalists but warrant officers are specialists. Becoming a warrant officer lets one continue doing the same type of task for a whole career. An officer may lead a platoon, then be a S-3 for a company, then spend some time recruiting, then lead a company, then go back for more schooling, then be an S-4 for a battalion, then serve in a Pentagon desk job, then teach at the Academy,..., but a warrant officer generally does the same thing for his or her whole career, by choice. Typically it's a more technical type of job.
The Air Force (and hence Air National Guard) doesn't use them, by choice. The "warrant" originally meant being appointed an officer by warrant of a government official (in the U.S., the Secretary of the Army, etc.) rather than commission by a head of state. They appeared first in the European navies, which needed them as technical specialist. Fletcher Christian of the H.M.S. Bounty was a warrant officer as master's mate, not a regular officer of the British Navy as Lt. Bligh was. Typically a physician, carpenter, etc. might also be warranted by the ship's captain, who also enlisted the crew.
Be careful! Many services did away with this as a third cadre. In the U.K. army, for example, a warrant officer is a sort of super-sergeant, but still enlisted. Other countries made it the most junior commissioned officer rank, though many have since dropped it.
For your friend, it's better pay, a higher rank (above all enlisted personnel), and makes it easier to become an officer if desired some day. The big reason to d it would be if he really knew what he wanted to do in the Army and wanted to be sure to be able to keep doing it for the rest of his career. Other risks vary with the specific specialty chosen. The slight career risk: If, as happened near us twice recently, the guard/reserve center has its mission changed and begins doing something wholly different, it might be easier for him to change tracks as an enlisted man than as a WO, depending on many factors. The other issue is that many people, like you, don't know what one is, so it may be harder to explain to a civilian employer how that experience is relevant.
In general, for a bright person with some leadership and technical potential who really enjoys a particular aspect of his job, and who doesn't mind being 'typecast', this is a great deal and to be encouraged.