The 1cyclopedia

? Block Has groovy things, like coins, or mushrooms or fire flowers or starmen.
1-up An extra life.
1-up Mushroom Gives you an extra life. Is orange with green spots.
10 Coin Block A ? Block that has ten (or more) coins in it depending on how fast you are with the A button.
Big Mario A bigger version of Small Mario.
Blocks Smash them for 50 pts.
Blooper White squid-like creatures in the water levels.
Bonus Worlds Places either down in the underworld or up high in the sky filled with coins.
Bowser The guardian at the end of the castles. The last castle has the real Bowser in it.
Bullet Bill Comes out of the cannons to try and kill Mario.
Buzzy Beetle A beetle with a fire-proof shell.
Castles Worlds x-4. At the end is a Bowser.
Cheep Cheeps Fish that are in the water levels.
Coin The round, yellow things. Grab 100 for an extra life.
Fire Bar These are rotating fire bars. Do not touch.
Fire Flower Gives Mario the ability to become Fire Mario.
Fire Mario Mario can shoot fire in this mode by pressing B.
Flagpole Thing you jump on to end the level.
Goomba A brown (blue in an underworld or white in a castle) creature to stomp on.
Hammer Bros. These creatures come in pairs and throw hammers at you!
Koopa Bowser's last name
Koopa Troopa Turtle-like creatures.
Koopa Paratroopa Koopa Troopas that can fly.
Lakitu This guy in a cloud throws spiny shells at you.
Lava What is in the holes in the castle levels.
Lives Chances to complete the game.
Luigi Mario's brother, is playable as player 2 in a 2-player game.

Minus World Probably the most famous glitch in history. How to get there. Fun fact: If you get a game over in the Minus world, you can use the continue trick to get back there!

Mushroom Makes Small Mario Big Mario.
Mushroom Kingdom Place in which all 8 worlds take place in.
Pipe Thing to go down sometimes.
Piranha Plant These plants with teeth periodically come out of pipes.
Princess Toadstool Lady held captive by Bowser. The whole reason for this game.
PodobooThe fire that jumps out of the lava.
Retainer see "Toad"
Small Mario What you start out as. Neither big nor has special fire-throwing abilities.
Starman Grab this to become invincible for a small period of time.
Toad Greets you at the end of every castle except the final one with "Thank you, but our princess is in another castle!"
Trampoline This bouncy thing takes you to new heights.
Vine Thing to climb to get to the bonus worlds.
World Division of the game. There are 8, each ending with a castle.