Difference between these ability events

[HellslayerX15]

Whats the difference between the events:

a unit -
begins channeling an ability
begins casting an ability
starts the effect of an ability

I especially cant find any difference between the first ones

 

[HaniBon]

begins channeling an ability
begins casting an ability
starts the effect of an ability
----
1: When a unit is channeling an ability, it is canceling an already casting spell (example is Starfall)
2: Before an unit has used mana etc, just clicked the button for the spell
3: When a unit has selected a target with the spell and the spell has drained the mana and triggered the spell

 

[HellslayerX15]

Didn't get the first one at all but the main thing is that i now know that the 3rd suits my needs the best

 

[HaniBon]

If you are casting Starfall (starfall is an Channeling-type of spell. If the unit gets Stunned or such, the spell stops casting), so when a unit is Channeling a spell, it is stopping an Channeling-type of spell, such as Starfall...