Interesting that the newbie initiative would have you buy and sell tokens on the hive-engine. I say that because the Hive-engine is very important as a tool to get your asking price for a coin when speculating on a coin's price but there are better tools for simply converting from one coin to another. As you noted your hive-keychain can do the same task more easily for a simple buy/sell but hive-engine means you can wait to get your desired price on a buy/sell (if you are willing to wait).

As for tribes and tokens there is a little more to it than that. Any person can make a token if they wish to pay the fee involved. I've done just that with the GLD token. Sometimes the token is used to support a community (like my $GLD token with the #earnspendgive community), sometimes to support a tribe (like $SPT for Splinterlands or $AFIT for Actifit), but sometimes they are for specific uses within a tribe such as SPS and DEC within the Splinterlands game.

Communities and Tribes can have different levels of Hive feel. Hive Learners is very social network based and would be a community. Splinterlands is very game like and would be a tribe. Actifit functions both as a tribe and community so maybe a hybrid of both :)

As you said....Hive is vast :) There is Hive the crypto backbone. Hive the social media site. Hive the dApp engine. Tribes that are purpose built communities which may or may not appear on the social media site. Communities which are like tribes but not actually set themselves apart as much as a tribe.

All very frustrating :)

Good luck on your journey!