What is a top-level domain (TLD)? Well, it’s the “.com” bit in google.com.
Why is it important? Because, generally speaking, it tells you something about the domain. “.com” is short for commercial, indicating abusiness of some kind. “.gov” Exists for government, and we even have country-code TLDs, see “.eu” or “.us”.
Some applications of these are used in multilingual sites.The “.us” and “.uk” versions of sites will use the respect region’s spelling ofwords, for example (color vs colour).
Other times it can indicate that you are a technically inclined business, perhaps with a “.net” or a “.io” address. This one inparticularly is interesting, because the “.io” address is actually a country code that’s been adopted by the tech industry, because here in tech land IO means “input/output”.
More technically, there are several TLDs that indicate infrastructure domains, used to maintain the internet. These either function as “road signs” so to speak, pointing computers where they need to go, or perhaps hold essential data that helps in managing that traffic.
Your TLD is something to consider. Do you need to give off a certain look and feel with it? Do you need to show you’re an official organization of some kind? Do you want to be clever and make TLD complete the name?
In general, your TLD isn’t going to be an SEO impact. The impact from there is more to do with memorability, or ease of access for users who are manually typing the domain. But it is another aspect of your branding to consider.