Q:

Terraria map explanation

I generated my Terraria map using MoreTerra and TerraMap and below is the image of the full map:

From the left what I see is, Ocean, Forest, Dungeon, Forest, Snow, Forest, Desert and so on. However, I do not see Crimson or Corruption. Are those missing in my map or are they available after progressing through the game?
Can someone point it?

A:

Corruption is that purple tunnely bit to the left and inside of the snow (see the map view on the wiki page, note you will probably get purple ice as well).
Crimson won't appear on this map as it is either crimson or corruption generated per map (First sentence in the link explains this).
Your map biomes
I would say it goes:
Ocean, Forest, Dungeon, Corruption, Snow (+ 2 Floating Islands above), Forest, Desert, Forest, Jungle (+ 1 Floating Island), Ocean.
Note many of the biomes also have a "deeper" biome section where there would be new enemies and treasures etc. to spawn.

