Creative Mode
In creative mode, you are invincible, you can fly, and you have complete access to the creative menu. In the creative menu, you have access to all of the blocks and all of the items you can get in Minecraft. You can do whaterver you want in creative mode. You could create a house made out of diamond blocks, a redstone contraption, or even an adventure map. It's all up to you about what you want to create!
In the image to the right, it shows the "Building Blocks" category of the creative menu. The blocks shown here are some of many of the blocks in the game!
Survival Mode
In survival mode, you have limited health and limited resources. Unlike creative mode, you will have to craft using a crafting table to make the blocks and tools you need. To make one, all you need is to chop down a single wood block, craft it into wooden planks using your personal crafting grid, and finally craft a crafting table using that grid in a 2 x 2 formation. This is important because it is needed to craft over 80% of Minecraft's blocks and items!
You will also need food to stay alive, tools and weapons, and other ultility blocks. By doing all of these things, it will ensure a better survival experience. Also, hostile mobs will spawn at night. If you are planning to sleep, mine, or work on a building project make sure to light up the place. Otherwise, you will have to fight them for their drops!
In the image above, a player shows his farm in his survival world.