NN wrote "If you buy a domain from someone other than your webhost, you will need to learn about DNS records. "
Your hosting firm should give you two (or more) nameservers, and the firm where you registered the domain name should offer a control panel where you can set the nameserver names, eg
ns1.vfm-hosting.com ns2.vfm-hosting.com
You don't need to learn anything about the DNS records (they're going to be managed by the web hosting firm).
Keeping the hosting separate from the domain registration firm means I can switch registration firms whenever I want (eg if one has a low cost deal for domains to be transferred into their service) without changing the hosting arrangements.
While domain registrations are in periods of one or more years, web hosting can be had for much shorter periods and sometimes it is worth starting by renting hosting for a month or quarter (so you don't pay out a lot, and then find they are unreliable or don't offer some facility you want to use), so changing hosting company without changing the domain registration firm can be useful if you start to add extra areas to your website.
Say you wanted to add podcasts or have video clips for relatives abroad to see (hidden away in a subdirectory so only visible via web link you send in an e-mail). Some web hosting firms have limits or restrictions on how much traffic or what types of file can be stored, so you may wish to switchi hosting company part way through a year.
(Not really applicable to this thread, but for someone setting up a website to hold photo albums and video clips from holidays, or to show the new baby, for example, it can be worth thinking about flexibility).