It depends on your outsider. A normal internet connection goes from your client (like a browser) to an endpoint (like a website).
The ISP as well as the endpoint knows your IP address. However when connecting through the ISPs network through a website you often have additional routers on the path, big internet exchanges ... Just do a traceroute from your home IP to some website and you often get half a dozen hops or more.
So everyone with the ability to sniff on or between these hops could possible know where you connect to. The more close to your home the more likely they can see all the endpoints you connect to.
Assuming a local ISP or your countries three letter agency, they can see the domains (or IPs in general) you visit, when you visit them, how long you visit them, the amount of traffic exchanged with the endpoint, the OS and applications you use, the protocols you use and in case the protocol does not use encryption they can also see the content.
Based on that, they could make some assumptions what URL you visited and what you are doing online in general and how your soft/hardware stack looks like.
With encryption they can't directly see the content by just passively looking at the traffic. They could start active attacks which generally are a bit more noisy to see your content.
Also they could attack the endpoint itself to see what you are doing.
On IPv4 MAC addresses are not transmitted outside your local network. On IPv6 this is more of an issue.