Bicycle components actually include all the parts that make up your bike. But, the parts that wear or are used for powering, steering, or braking deserve the most attention by far. You can ride for years and not change non-moving parts like the frame, seat post or handlebars.
The parts that make up the drive train like the chain, sprockets, deraileurs, cassettes, chain rings, and hubs etc do need to be replaced from time to time depending on how much you ride, riding conditions and how well they are maintained.
So, it’s a good idea to purchase a bike with components from a quality manufacturer. And, availability of replacements can be an issue as well. For the vast majority of bikes the supplier of choice is Shimano. They have been in business for almost 90 years (over 50 years in the US). They are recognized as quality parts and replacements are available worldwide.
I have been using bikes with Shimano components for 15 years and am very pleased with the results. If I buy a new bike I, and just about everyone I know, look for the Shimano name.
For high performance bikes the supplier of choice is Campagnolo. They have been around even longer that Shimano, and are more costly, but for serious competition riders it is well worth the price difference. They are found, almost exclusively, on high end performance bikes where strength and weight are critical. Availability is good on these as well.
Don’t be fooled by fancy looking bikes with cheap components. Look for parts that will serve you well on the long haul. You will be glad you did.