Your monster's type is actually quite important in MonBre. 'Pro' is the advantage the type has, 'con' is the disadvantage. Role is a suggested role you would choose the monster for. There are five types and another SUPER SECRET CRAAAZY type.

Evil
Pro: Get a lot more of an SRP bonus per evolution than others.
Con: Sap half a percent of life a day from the breeder.
Role: Combat! Make for great splicers and fighters. A lot of their abilities are offensive, to the point where the best self-heal for them would be the worst for a good type monster.

Good
Pro: Heals half a percent of life a day for the breeder, lots of good healing skills.
Con: Gains fewer per evolution.
Role: Definitely good party support and have access to paladin-like skills.

Worker
Pro: Less likely to be injured when working, unaffected by work-level limits.
Con: Eats twice as much a day. (caps at 400/day at adult)
Role: More of a worker by the side to gain money and use in splicing. Skills tend to be passive buffs and energy management.

Cute
Pro: Eats half as much. Lots of party-wide buffs and passive buffs.
Con: More of a chance to be injured when working.
Role: Pet. They're cute and cuddly, and don't take up many resources. They have normal combat capabilities, so they're fine fighters.

Normal
Pro: A small advantage: +3% inherent crit chance.
Con: No pro.
Role: If you can't make up your mind, or want to be more flexible with your monster, this is a good type. They have skills ranging in all categories.


Evolution

So! Monsters evolve. When a monster in MonBre evolves, the look and attributes of the monster change. When the monster is at the right level (not combat power) it is ready to change into its next form! When you evolve, you can receive a new ability. Also, monsters may still evolve if you give them enough time... but this is quite long - with adult level meaning you wait 31 days - so it's best to level manually.

Level
Egg -> Baby
Instantly hatches within roughly 10 minutes.
Baby -> Toddler
Level: 10
Toddler -> Child
Level: 50
Child -> Teen
Level: 150
Teen -> Adult
Level: 250

Age
Egg -> Baby
Instantly hatches within roughly 10 minutes.
Baby -> Toddler
Age: 1 day
Toddler -> Child
Age: 5 days
Child -> Teen
Age: 16
Teen -> Adult
Age: 31

Helpful Chart
The following shows how each of the monsters evolve. This shows only one evolution tree; they all follow the same formula, except the super secret monster, who just has a single path.

IMPORTANT: You have to MANUALLY go to the lab to evolve them. Do not forget this.