A chainsaw is ultimately a fairly straightforward piece of power equipment.
Engine. Bar. Chain.
However, most homeowner gas chainsaws contain a collection of features you'll need to consider before making a purchase.
Manufacturers design homeowner-grade chainsaws with the inexperienced user in mind. So you will find plenty of safety and ease-of-use features on these chainsaws.
Many gas chainsaws feature two-cycle engines. Two-cycle (or 2-stroke) engines require a mixture of gas and oil in the gas tank, supplying both fuel and lubrication to the engine during operation.
Essentially, you are "changing the oil" every time you gas up your chainsaw. This means you won't have to perform separate oil changes on your chainsaw like you would with a car; you'll just pour the combination gas/oil fuel into your tank and you'll be all set. Consult the owner's manual to get the precise recommended ratio of gas to oil for your model.
Across grades, chainsaws have pretty consistent weights. The constant vibration of the saw is what really wears you out.
Look for a model that features vibration dampening to lessen your fatigue. Many homeowner grade models include this feature, making it much easier to use the saw for an extended period of time.
Due to the constant metal-on-metal friction between the bar and chain of a chainsaw, the bar needs to be continually lubricated with oil. This allows the chain to run smoothly. Without it, chains can easily break.
Look for a chainsaw with an automatic bar oiler, which automatically applies oil to the bar as needed. If you don't have an automatic bar oiler you will have to work at a slower pace and be diligent about stopping to oil the bar.
An inertia-activated chain brake is one of the best safety features available on any chainsaw. Look for a saw with this feature. It will reduce the risk of injury caused by blade kick back.
When the nose of the bar comes in contact with an impediment such as a knot, it can kick back, usually down towards the operator's legs. The inertia-activated chain brake senses the kick back and stops the chain, keeping catastrophe at bay.