I just started using the Tor Browser and Orbot on my smartphone and would like to find out what I can do with it. Is there a lot of different Legal and Illegal services?
according to RFC 7686
.onionis reserved and so it can't be registered.
.onionis reserved in conjunction with Tor, not any other domain!
.onion-domains are self-governing resp. self-authenticating because there is no central instance to register a domain, and there is also no DNS. - thus the "names" are not so easy to remember.
to resolve an
.onion-domain resp. reach its site and view it, you need a Tor client (as you obviously know).
there are also gateways (Tor2web) to view
.onion-sites with normal clearnet-browsers, but it is not advised to use them (except you really know what you are doing) because you are still in the clearnet and not anonymous!
in the deepweb you can use normal clearweb search engines, which also provide a hidden service... but hardly any of them will give you hidden services as results.
thats the point where you have to use one of the deepweb search engines which searches the deepweb...
additional: there are also directory/index-sites in the deepweb and clearnet, which collect useful links to several hidden services:
See Tor's address spec.
So, yes, at this time,
.onion is the only TLD that is dedicated to Tor.
domains finishing with ".onion" can be visited with Tor software, for example blabla223344.onion means you can visit this website with Tor software. well, you can visit website of wikileaks or theintercept and they have URL for visiting their websites with Tor software, but you can also use ahmia.fi - a search engine, the same as Torch. for example, I just visited wikileaks and they say wlupld3ptjvsgwqw.onion is their website behind the tor network, when I tried ahmia.fi the first link was the same wlupld3ptjvsgwqw.onion