BBC (Blade Brake Clutch): A mower with BBC (sometimes known as Roto-Stop) has the ability to rapidly stop the blade from turning whiles keeping the engine running. This is handy for when you just want to empty the grass box, or transport the machine from one area of your lawn to another without having the blades turning. NOTE: Just because your machine is fitted with BBC or Roto-Stop, please don't think it's safe to put your hand up the chute to clear clogged grass, it's not safe to do this, and you could still loose fingers or worse if you do. Please be warned.
Chassis / Cutting Deck/ Mower Deck: This is the body of a lawn mower where all the components that make up the mower are housed. lawn mowers will either have a metal deck (sometimes referred to as steel or tin deck, or moulded aluminium). Quite a few machines now use a decks made from robust plastic, or poly, which is pretty resistant to impacts, rust and corrosion. Steel / Tin decks suffer from rust, whilst Aluminium decks can suffer from corrosion, especially if not cleaned after use. Always clean your mower regardless of what it's made from, if you want it to last.
Collector / Collection Bag / Grass Box: The container which would commonly attach to the back of the machine to hold the grass cuttings, or if you like, clippings. Some ,made of a steel frame covered in a replaceable fabric, some are made from moulded plastic. Fabric versions can / will clog and block airflow after time so will need to be periodically washed out and dried before use. Plastic collectors tend to be easier to maintain, and because they use ventilation holes or slots don't tend to block up so easily. Plus you can just hose them out if need be.
Cordless: A lawn mower or other power tools powered by a rechargeable battery are refereed to as Cordless. Seems to be a growing trend now to move to a cordless machine, whether it be a mower, Strimmer, or chainsaw, the range of equipment is evolving fast, and the technology is ever improving. Nowadays virtually any garden equipment that had a petrol engine on it can now be found in a battery powered version. As it stands at the moment some of the cordless stuff out there is a quite pricey, and I'm guessing that will change as the popularity in cordless gear increases.
Electric Equipment: An electric or mains powered equipment, is exactly that, it's it's plugged in and powered by your mains electricity supply. Downsides: You have to drag a mains cable around with you. it's mains electricity, can be dangerous if used in a badly maintained state, exposed wires etc. Always keep mains lead in good condition. Always use outdoor mains equipment through a RCD (Residual Current Device) for your own safety.
Hand Mower: A hand mower requires no electric or petrol power. You push the machine along, and the wheels drive the cutting blades. OK for a very small area of lawn where a bigger machine just wouldn't be practical.
Hover Mowers: Hover mowers literally float on a cushion of air, and have no wheels. These machines are less common nowadays, but still have their uses for steep banks etc..
Key Start, or Electric Start: An electric start machine has a battery and a starter motor, much like your car does, and it makes for easier starting without the hassle of pulling a rope. Some of them do recharge the battery while using the machine, and some, especially the more modern ones require you to re-charge the battery yourself.
Mulching or Recycler Mowers: This type of mower usually will have a different blade setup than a standard mower, and will have a blade shape which will have multiple cutting edges at different heights. The deck will normally be slightly more enclosed around the blade. The idea here is to chop the grass cuttings into smaller pieces and propel them back onto the lawn where they will get reabsorbed. No collection box required, but you do need good conditions to operate them in.
OPC: All modern petrol mowers except BBC equipped models come with some sort of OPC system. OPC stands for "Operator Presence Control" Before you can even start the engine you'll have to hold the OPC lever in the run position, if you let go of this lever the engine will stop. It's there for safety reasons, and you'll have to stop and restart the machine every time you empty the grass box.
Push Lawn Mower: A basic mower which you have to push manually, it has no self drive to the wheels.
RCD: (Residual Current Device) Any socket you plan to use to plug in a lawnmower should have RCD (residual current device) Protection. If your home is older and doesn't have this protection built in you really should purchase a RCD Adaptor Plug. The RCD is a life-saving device that protects against dangerous electric shock and reduces the risk of electrical fires.
Roller Mower: These lawn mowers would have a roller on the back and wheels on the front. Rollers can either be plastic, or metal depending on brand or price. Roller will give you those stripes you see on some lawns, and also help with mowing over the edges without fear of scalping the lawn.
Ride On Lawn Mowers / lawn tractors: Ride on mowers are ideal for large areas of grass or lawns where walking with a small mower wouldn't be practical. These machines come in various cutting widths usually much bigger than a walk behind machine, and get the job done much faster and easier. Grass collection on these machines also differs from make to make, but usually it'll be either Vacuum or Sweeper.
Self Propelled Mowers: A self-propelled lawn mower is one that propels itself along usually providing power to either the rear wheels or roller. There are some that drive the front wheels, and even some that drive all four (AWD).