>>55276895Generally hebe in this context refers to the type of loli that has begun developing visible sexual characteristics. Typically they look like they're in their early teens and have aspects like budding breasts that hint at being in early puberty. Unlike loli (which is purely a body type thing), hebe is heavily implied to also be age-related, and as a result the characters in question have to be in their early to mid-teens.
Most female Pokemon protagonists, and by extension most rivals and other characters like that fit this. Examples outside of Pokemon would be Megumin from Konosuba or
Someone like Tatsumaki from One Punch Man is not a hebe even though she has a comparable body to someone like Megumin, because of her age.
Pokemon has surprisingly few non-hebe lolis, but for an example of a loli that isn't a hebe in Pokemon, consider Acerola. If you compare Acerola and Marnie, you should have a good understanding of what makes a hebe different.
Note that every character mentioned in this post would still classify as loli.