• Mechanized infantry are infantry equipped with armored personnel carriers (APCs) or infantry fighting vehicles (IFVs) for transport and combat (see also mechanized force).
• Mechanized infantry is distinguished from motorized infantry in that its vehicles provide a degree of protection from hostile fire, as opposed to “soft-skinned” wheeled vehicles (trucks or jeeps) for motorized infantry.
• Most APCs and IFVs are fully tracked or are all-wheel drive vehicles (6×6 or 8×8), for mobility across rough ground. Some nations distinguish between mechanized and armored infantry, designating troops carried by APCs as mechanized and those in IFVs as armored.
• The support weapons for mechanized infantry are also provided with motorized transport, or they are built directly into combat vehicles to keep pace with the mechanized infantry in combat.
• For units equipped with most types of APC or any type of IFV, fire support weapons, such as machine guns, autocannons, small-bore direct-fire howitzers, and anti-tank guided missiles are often mounted directly on the infantry’s own transport vehicles.

Source:Wikipedia