A domain name is the alphanumeric location of a person or organization as they appear on the internet, either through a web URL or an email address. A domain name's IP address is the numeric digits attached to that. So domain names are the more "user friendly" version of the IP address that the DNS has attached to it. Source
TLD (Top Level Domain, which is the extension after the dot of an domain name)
Second Level Domain, which is the part before the . of the extention of the domain name. This is what is attached to your email address.
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An IP address is the unique Internet Protocal for each device (smartphone, Alexa, tablet, computer, laptop etc.) connected to the internet. Source
IPV4 is orginal possibilities of IP addresses (about 4.3 million). However, as the internet grew, they have been fully allocated to ISP's and users. So IPV6 came along to allow for a much larger pool of IP possibilities (enough for everyone!). Source