arkham-starter.com | Explore Investigator Expansions
Other than the menu, this page exists to host the explainer image below. You are free to hotlink to this image. It is such a commonly confused topic for newcomers. So, what exactly is this madness?

Previously, FFG releases new campaign in 1 + 6 bits as highlighted in green squares. The first one being a box labelled as the campaign name. Perhaps you thought it is an entirety start-to-finish of a new adventure, but actually it is just 2 scenarios out of 8. The end of the first box left you hanging, waiting for scenario 3 and beyond.
Then each month, 1 scenario each time + a bit more player cards to use would came out as blister packs successively. In this sense you are subscribed to the drip-feed adventure and look forward to the next episode, and they hope it became a part of your lifestyle, so they dubbed this "living" card game. (LCG)
Though that sounds fun in theory to go to shop to get the blister packs each month, it is a pain in many ways and sometimes go against how the game works (smell like mainly a marketing reason, which now start to backfire when new player comes in and trying to get the campaign is not the latest release one, it is only "living" when it is the latest one.) so they change the dimension of selling the expansion in blue rectangles now.
You should get the new format, but the box can sometimes confuse you, thanks to the artwork of old 2-scenario box happened to be the same as the new Campaign Expansion one. I would say this more convenient new release format stops being worthy of a special "LCG" labelling and should be called just a regular game expansion like other boardgame expansions, but they are still rolling with this LCG wording since it was with the game from start. (so it maybe safe to not exactly know what is an LCG from now, just "expansions".)