how to tell whether a summon is inherent or an effect, and why it matters.
Inherent summons are XYZ summons, Synchro summons, or Special summons via a condition on a monster card. For example, Cyber Dragon: "If your opponent controls a monster and you control no monsters, you can Special Summon this card (from your hand)." As you can see, the condition is listed on when you can special summon. This is not an effect.
Effect Summon are monsters special summoned by a card effect. These include Fusion summons, monster effects that summon an additional monster, or card like Monster Reborn/Call of the Haunted.
The easy time to tell is when its something like XYZ summon vs Monster reborn. obviously inherent vs effect. Harder ones are like Tragoedia, Gorz, Chaos monsters, REDMD, Lightpulsar's effect to summon itself from the grave, or Photon Thrasher.
To tell if its inherent or an effect, check the effect and look for a : or ;. if there is a ; that means that it is an effect with a cost(everything before the ; is the cost, everthing after is the effect). If there is a :, then everything before is the trigger, everything after is the effect.
so lets look at tragoedia: "When you take Battle Damage: You can Special Summon this card from your hand." there is a :, this means that it is an effect. The trigger is taking battle damage, the effect is to summon itself.
Gorz: "When you take damage from a card your opponent controls: You can Special Summon this card from your hand. You must control no cards to activate and to resolve this effect." this one is really easy because it actually says you must control no cards to activate this effect. given that effect is in it, its obviously an effect. Even if it didnt say that, we would know because of the :.
Chaos monsters(lets use Darkflare): "You can Special Summon this card (from your hand) by banishing 1 LIGHT and 1 DARK monster from your Graveyard." You notice there is no mention of it being an effect, there is no ;, and there is no :. This means it is an inherent summon and not an effect.
REDMD: "You can Special Summon this card (from your hand) by banishing 1 face-up Dragon-Type monster you control" Clearly there is no ; or : and therefore is inherent.
Lightpulsar from grave: "You can Special Summon this card (from your Graveyard) by sending 1 LIGHT and 1 DARK monster from your hand to the Graveyard." Again, no ; or : so it is inherent.
Mermail AbyssMegalo: "You can discard 2 other WATER monsters to the Graveyard; Special Summon this card from your hand" Because of the ;, we know its an effect. We know that discarding is the cost, and summoning is the effect.
Now that we know how to tell whether or not an effect is inherent, lets go about seeing why it matters.
If a card says "negate the summon" it can only negate an inherent summon. For example, thunder king can only negate an XYZ ,Synchro ,or inherent summon like cyber dragon or a chaos monster.
Laggia vs dollka: Laggia can negate a summon. This means he can only negate inherent summons. Dollka says he can negate an effect. That means he can negate monsters like trag or gorz, but not ones like lightpulsar or darkflare.
Solemn Judgment vs Solemn Warning is an interesting one. Judgment can negate an inherent summon only, however he can also negate a card like monster reborn to stop a summon. Warning on the hand can not only negate inherent summons, but he can also negate any effect which would summon a monster. this includes reborn, coth, lightpulsar, redmd, and so on.
Hope this was helpful! as usual, please ask anything confusing or if you want help for specific situations.