The line drawn between powered armour and combat walkers is vague, to say the least. Generally speaking, if there is only one crew member, it's categorized as powered armour. If there are two or more crew members, or if the operator sits in a cockpit rather than being strapped into a waldo array, then it's a combat walker. Since some of the bigger powered armours are actually larger than some smaller combat walkers, the distinction is largely arbitrary.
The range of applications for which powered armour is employed is very wide, and they can be adapted for almost any sort of terrain. The only area where they fall down is in areas with restricted access, such as ship or building corridors, or in heavy vegetation, due to their size and weight. Even the lightest suits available mass more than a ton with a full battle load, and a heavy battlesuit can mass as much as seven or eight tons.
Suit functions are normally controlled by a low-grade AI, which is in turn guided by the operator. A direct neural link between the wearer and AI is normally employed to achieve the finest degree of control possible, though some suits can be manipulated manually or by voice control with an inevitable degradation of performance. A standard skull-plug is quite obvious; it's difficult not to notice a pair of 5cm stainless steel interface sockets in someone's temples. The better (more expensive) skull-plugs are not too difficult to conceal from casual inspection, though they do show up on any sort of body scan. The stigma which applies against cybernetic body modifications on many of the core worlds has limited the common use of these very useful pieces of equipment, and their industrial counterparts, within the Oikumene, but they are extensively used by the Patrol, Free Traders, and (of course) Beyond. Those workers who are employed to operate them on the Core Worlds are generally paid quite well, to offset in some measure the opprobrium they must endure from the general populace if and when their modifications are discovered.
Private users should be aware that powered armour and combat walkers are classified as military vehicles, and most planetary authorities will therefore require that the weapons systems be disabled and certified as dormant while within their purview. Private ownership of active suits is heavily restricted through most of the Oikumene, though there is a small collector's market for them.
The Zephyr is a relatively light-weight adjustable powered combat suit, designed with close-range combat reconnaisance in a wide range of combat environments in mind. It is reasonably nimble and speedy, and mounts a jump-jet as standard equipment, allowing the wearer to leap tall buildings in a single bound. It can be hermetically sealed against chemical or biological agents, and can operate with either a self-contained breathing system, or a comprehensive filter and scrubber array. With a bolt-on oxygen supply and maneuvering thrusters replacing the jump-jet, it can be used as a hardened vac-suit for use in zero-gee conditions. The structure of the suit is compartmentalized, and the suit can be configured to seal off a punctured compartment to minimize leakage.
The DEF 8 "Polysteel-Plus(tm)" armour is light-weight, but is adequate against most small-arms fire. The armour base can be supplemented with reflec or ablat panels (but not both).
It's weapon load is light compared with that of a fully-fledged Battle Suit such as the Typhoon, but is nevertheless substantially more potent than many conventionally portable systems. A standard battle load consists of a forearm-mounted plasma blaster on one arm, a forearm-mounted micro-missile launcher array on the other, and shoulder-mounted grenade dispensers which are normally used to dispense smoke or anti-laser chaff. One targeting laser is mounted with a video input over the crown of the head-piece, and another alongside each of the forearm mounts allowing minimal exposure while firing from cover. In common with the heavier battle suits, in the Zephyr it impossible to use the hands for tasks other than suit control, though the waldo claws are moderately sensitive, and a skilled operator can use them almost as well as his or her own hands (minus 2 - 5 to DEX-rolls for any task requiring manual dexterity).
Though it has been superseded in first-line military service by more recent models, the Mk.III remains in occasional use for police or security applications, or as H.E.L.S. (Hazardous Environment Life Support) for locators and the like. The Zephyr Mk.III is no longer in formal production, but there is a reasonably ready supply of spare parts available, and its civilian use has resulted in a modest after-market modifications industry.