Codes are one kind of secret presented in plants vs. zombies
They generally exert no impact on your normal game journey, just for appearance.

You need to input every character in codes consequently to enable the corresponding function
For eg, to enable "future", you need tap "f" "u" "t" "u" "r" "e" on your keyboard consequently, in any interface, whether the main menu or in levels. When you hear a special sound after input every single word, you achieve.
To enable the type box using controller: "LB" "RB" "LT" "RT" for xbox, and "L1" "R1" "L2" "R2" for PS

Here is the code list:

• "future" gives zombies future sunglasses
  
• "mustache" or "moustache" gives zombies mustaches
  
• "trickedout" alternates appearance of lawn mowers (pool and roof cleaner would not be effected)
  
• "sukhbir" alternates zombies' call for brains
  
• "↑↑↓↓←→←→BA" alternates sounds in Choose Your Seeds screen

And, there are codes whose availability has to do with the tree of wisdom :

• "daisies" leaves daisies when zombies die, available after the tree of wisdom reaches 100 ft
  
• "dance" makes zombies dance, available after the tree of wisdom reaches 500 ft
  
• "pinata" brings a shower of candy when zombies die, available after the tree of wisdom reaches 1000 ft

By the way, except told by searching online, the tree of wisdom sometimes tells you information about codes, including "mustache" and "trickout"

And, there's also an achievement related to codes: get Ask Me About Mustache Mode achievement after firstly starting it.
https://steamuserimages-a.akamaihd.net/ugc/1995687607715797296/5D39B1C39B1B98A7D2CF357A33822F88F9256FFD/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

To close the effects brought by codes, just repeat it once more.

Some of the information comes from Plants vs. Zombies Wiki provided on FANDOM
And, enjoy the game, thx 4 reading