I am using Tor browser to browse, and download things. My question is: If I visit a website using Tor browser, then who knows, or who can know, that I am using Tor browser? And what will he get? That is, will he know what websites I browsed using Tor, or only the information that I am using Tor?
Your ISP knows that you are using Tor. But it doesn't know specifically that you are using the Tor browser, except of course if you just downloaded it. Also, your ISP may share that information with other potential adversaries.
However, your ISP does not know what websites you visit using the Tor browser. Neither do the first two relays in circuits that your Tor client creates to reach them (entry guards and middle relays).
The Tor exit relay in each of those circuits does (of course) know what websites you visit through it. However, it doesn't know who you are, unless you reveal that information in the process. Given that, it's important to always use end-to-end encryption, HTTPS for websites and TLS for email clients.
Websites that you visit know that you're using Tor, because there is a public list of relays (excluding only bridges). However, websites don't know who you are, unless you reveal that information to them.
The EFF made a clickable diagram which illustrates what your ISP (and other parties) can see when you browse the web using Tor and/or HTTPS: https://www.eff.org/pages/tor-and-https