What is ...? 

What is a CCG?
CCG stands for Collectible Card Game. A card based game with an added feature of  collectibility. It's something like poker meets sports cards. There are a lot of CCGs out there. Some are based on books (e.g. Lord of the Rings, Wheel of  Time) Some are based on TV or Film series (e.g. Star Wars, Star Trek, Highlander, Pokemon). Some have original stories or concepts on their own like the first CCG, Magic the Gathering.

What is a Starter, Boosters, Base set, Expansion set...?
A Starter is a deck of cards designed to make you play right out of the box. It is also called Starter Pack or Starter Deck. 
Boosters are additional card packs which you can add to your starter deck to make it better. It is also called Booster Packs or booster cards.
Base Set or Base Cards are cards that come from the original set which is essentially the basic game. In MECCG that will be METW and MELE. 
Expansion Set or Expansion are a different set of cards that you may add to your base set. It usually expands the scope of the original game. It adds new cards and may also include additional rules designed to add more flavor to the game. In MECCG those will be METD, MEDM, MEAS, MEWH, MEBA.

It originally came out as Middle Earth:The Wizards(METW). There are five wizards in the game whose goal is to defeat the dark lord Sauron. Now the five wizards have a common goal but they don't necessarily agree on how to approach it. You play one of the five wizards and decide an approach to reach the goal. You try to get individual characters and groups of people to aid your cause. Along  the way you find weapons and items with powers to fight enemies like orcs, trolls, and powerful creatures like dragons and the Nazgul. Get allies like Tom Bombadil or Treebeard to aid you. Or help Aragorn fulfill his destiny of becoming King.
METW came in Starters and Boosters.

The second expansion was called Middle Earth: Dark Minions (MEDM). It added and introduced cards known as minion characters, servants of the enemy. You now get to play with characters that spy for Sauron ... oooh treachery is the worst enemy.
MEDM only came in Boosters. You need to have a METW Starter to play.

If you've read or maybe watched animated features of  The Hobbit and/or The Lord of the Rings (LOTR) think how fun it is to go to Rivendell and get the aid of Elrond. Go to Lorien and ask Galadriel and his husband Celeborn to aid your cause. Play as Gandalf,  go to Bag End and meet  Bilbo and Frodo. Find the One Ring and destroy it at Mount Doom. Sneak into Smaug's Lair and find his weakness and defeat him. Have Gimli and Legolas join your company  and fight orcs and trolls.

When Middle Earth: The Lidless Eye(MELE) came you were given a chance of playing not the heroic wizards and characters in your deck but the villainous Ringwraith (Nazgul) characters. Now you are playing one of the nine dark emissaries of  Sauron. Similar to METW where the wizards don't agree on the approach to use, so do the nine Ringwraiths. Your ultimate goal is to find the One Ring, not to destroy but to return it to your master Sauron, the Lord of  the Rings. 
As one of the nine you decide how best to approach this goal. No more heroic individuals and groups in your deck, instead you call on orc and troll groups to your cause. Instead of fighting off Smaug you ask him to help you, that's not easy but you can try. Oh by the way, did I say you can even play as Sauron, nasty. 
MELE came with its own Starters and Boosters. It was considered a stand alone expansion set. It can be played with or without having cards from METW.  That means if you MELE cards you can  use cards from METW and vise versa. You can play with or against someone who has a wizard/hero deck. Yes, you can pit your ringwraith and minion characters from MELE against wizards and hero characters from METW... fun, fun, fun!!!

Middle Earth: The White Hand (MEWH)  introduced the aspect of a fallen wizard. What's a fallen wizard? A wizard who has been corrupted. He  no longer wants the One Ring destroyed, He wants to keep it for himself. You get to have cards that allow you to play as a fallen wizard. We can't all be like noble Gandalf. Some of us want to play like sly Saruman.
MEWH came only in boosters. You need a starter from either METW or MELE to play.

Who makes the game? The game was published by Iron Crown Enterprises a game company which produced many Middle Earth based games.