A card text following the PSCT (Problem-Solving Card Text) has a structure that eases the reading of a card text. This structure is built in a basic format:
Activation Requeriment, Condition or Timing: Cost or target; Effect
Everything that is found before colon and semicolon isn't a effect.
Before colon we can find a Activation Requeriment, Condition or Timing of when we can activate that card. Follows below an example of each situation:
Activation Requeriment: "When this card is destroyed and sent to the graveyard:"
Condition: "Once per turn:"
Timing: "During either player's turn:"
Before semicolon we can find the cost that needs to be paid to activate that card or the target that needs to be chosen when that card is activated. We have some examples below:
Cost: "Pay half your LP;"
Target: "Target 1 monster on your opponent's field;"
Now let's read Solemn Strike's text effect:
"When a monster(s) would be Special Summoned, or a monster effect is activated: Pay 1500 LP; negate the Summon or activation, and if you do, destroy that card."
In Bold we have the activation requeriment, that is when a monster(s) would be special summoned, or a monster effect is activated. In italic we have the cost needed to be paid when Solemn Strike is activated.
The remaining text is the effect that will be applied when the chain resolves.