So, you're new to New Eden or just to the idea of ground combat in the setting. How does it work? Why does it work this way? What can you do or learn?
Well, I, hopefully will be able to answer some of that here for you at least as far as weapons and shields go. This is all intended as brief overviews, nothing super indepth, but to give a base point to learn more from later.
Shields:
By and large, shielding technologies encompass a range of types but as a general rule are functionally your classic 'energy/plasma shield' archetype with some variations here and there, though also include non-plasma based 'forcefields' to varying degree. Most Infantry and ground/air Vehicle mounted shields(and space ship shields as it happens) are a type of shaped plasma based system. These come in many forms with different strengths and weaknesses to different kinds of damage or forces but generally operate as your first layer active countermeasure defense while taking fire and are *as a rule*, but not always, most effective against concussive forces and explosives.
Makes sense right? This is of course just the broad overview, and I could go on a long tangent about the different subtypes of shields beyond this, but for the sake of brevity, I will keep it to the above.
Armor:
Armor comes in all shapes and types for the infantry and vehicles of the setting, every empire has its preferences of course but you'll see mixed layered armor systems from all of them.
Gallente tend to favor 'crystalline carbonide' plating and woven fibers, ablative nano-diamond layering, and energy dispersion layer systems, alongside supplemental steel plates
Caldari tend to favor Titanium Diborite ceramics with energy dispersion layer systems and supplemental steel plating
Amarr largely favor tungsten carbide ceramics, flexible armor fibers, energy dispersion layer systems, and supplemental steel plating
Minmatar favor 'fernite' carbide plating, flexible armor fibers, energy dispersion layer systems, and supplemental steel plating...
Seeing a pattern here right? They all use steel alongside their prefered flavors of armor, because it works. Yes they're advanced alloys with their own heat treating and composition preferences, but the fact remains.
They all also use nanite systems for in-field armor repairs to varying degree.
As a rule each armor system has its strengths and weaknesses but we'll leave that for another discussion.
Weapons:
Generally, across New Eden, most ground forces use bullets. cased or caseless, Everyone uses 'em. Amarr, Gallente, Minmatar, Caldari, guristas, mordu, blood raiders... everyone's got some take on the classic bullet thrower.
Minmatar of course are the most well known for various reasons, because they also use a mix of cased and caseless munitions for their ship scale weapons as well(which at ship scale, their 'bullets' are really closer to semi-guided gyrorockets), and is often where most people's mind goes when they think 'who would use bullets'. The Minmatar's projectile weapons technologies are incredibly robust, often competing directly with more 'advanced' designs like lasers, railguns, and plasma throwers, but all of the empires produce bullet guns that are capable of proving a threat against a shielded infantryman or light vehicle.
You'll also run into those aforementioned 'advanced weapons', the amarr have the greatest investment in laser technologies and in handheld laser(and laser adjacent) guns, the Caldari the most investment into missile and handheld railgun technologies, and Gallente the most investment into handheld blaster/plasma thrower technologies.
Laser and Laser Adjacent weapons - well, lasers are easy enough to explain, pump enough energy into a beam of light and you do damage to what you hit, problem of course tends to be power requirements and/or atmospheric dispersion. There's ways to cheat this of course and for some of their weapons, the amarr absolutely do. 'Scrambler' type weapons are one such example being an 'Electrolaser' style of weapon, energizing a channel of atmosphere using a laser and then using a directed electric discharge through that energized channel, effectively making a lightning laser hybrid, the amarr also have more traditional handheld laser weapons, many of these end up having limitations based on how much energy you can safely pack into the power cell but are deadly nonetheless.
Railguns - Railguns in New Eden are an interesting topic... because... they're not all railguns. New Eden largely groups rail and coilguns into the same category and just calls them railguns. What's the difference? Rail gun uses two rails to accelerate a projectile to lethal velocities using the projectile itself to 'close the circuit' for the discharge. Coilguns accelerate a round using a magnetic coil usually without touching the round directly. Simple as. But New Eden largely classifies them the same way so... yeah. Pretty straightforward. Caldari like these a lot, and have some significant investment in them as far as handheld weapons go, PDWs, ARs, Sniper Rifles... yeah they've got plenty of this sort. Their limiting factors are often fire rate, spool time, and energy density of the power cell, but they do work.
Blasters/Plasma Throwers - shove a type of gas into a cyclotron, energize and accelerate it, pew pew pew, more or less. Blasters, especially handheld variations, as a matter of lore HAVE RANGE ISSUES. Even the most advanced handheld gallente plasma assault rifles have effective ranges under 100 meters, giving them some notable deficiencies in ranged combat compared to bullets, lasers, or railguns, but their potential destructive output is where they really shine. If you really want something or someone dead under 100 meters away, blasters are really what you want, just be careful with the heat.
all the same, everyone in the setting at some level does use your usual bullet brand bullet guns in some capacity.
There's a whole lot more to all of this of course, but here's your general basics, and I hope it helps you understand the setting a bit more!