Today, there are two big families of armored vehicle, main battle tanks, light armor, and everything else. Main battle tanks are designed to sustain a hit from

Today, there are two big families of armored vehicle, main battle tanks, light armor, and everything else. Main battle tanks are designed to sustain a hit from ammunition designed to defeat armor, meaning sabot, RPG, anti-tank missiles, shells, etc. There are some classified techs related to this. Reactive armor is one part, anti RPG measures too (the think that shoots a RPG rocket before it lands). MBT can also land shot from very far away with its 120mm cannon. Most tanks built before the 80s are pretty weak against most RPG with directed charges. Light armors are designed to mostly sustain small arms fire (rifle calibers carried by infantry, anything smaller that 50BMG), and will shoot stuff like 20mm or 30mm, but carry armor that can't really defeat 20 or 30mm. "Everything else" will usually not protect against small arms fire (except those high mounted things who are designed to survive improvised bombs). I think MBT are built to mostly survive 30mm shells, but "not too many", and increase its chance or surviving shells and other things. The reason there are two kinds of vehicles, is because MBT are very heavy (50 tons or more) and can get stuck in mud, and because it's important to transport troops quickly and safely "enough" (unless you encounter a MBT, then you dismount and hides). But you should not really read everything that I just wrote, because I don't know what I am talking about.