What equipment is required to install a generator?
You need, at minimum, an interlock. That is a device which physically prevents the generator input and the main supply breaker from being on at the same time. Both can be off, but only one can be on. This is important for electrical line-worker safety.

If you buy or feel the need of an autostart generator, you will need to move loads to a sub-panel and have a transfer switch, so that the loads cannot overwhelm the generator when it auto-starts, and the transfer switch will automatically switch over (and serve the interlock function of keeping the generator off the main power lines.)

With a manual start generator and an interlock, you switch off most loads, start the generator, switch off the main, switch on the generator input, and can power anything on the main panel, but unless you have an absurdly large generator, not all at once. 

Which suits you better depends on both your mindset and cost-sensitivity. Even without the cost differential I prefer the flexibility of having any circuit available. Other people may prefer a fully-automatic switchover more.